W124 climate control vacuum pod replacement
 

Hi all, thought I'd share my recent foray into ACC repair:

Yesterday I replaced all the vacuum actuators (pods) for the climate control system in my sister's 1987 300D. Of the 6 total, only two are accessible without removing the dash - the pod for the floor vent flaps (pull the pushbutton unit to access this one), and the one for the defroster flaps (behind the glove box.) The other four - 1 center vent, 1 diverter, and 2 recirc - require pulling the dash. That means yanking the instrument cluster, steering wheel, p/b unit, glovebox, both lower trim panels, and then the whole dashboard. And then you need to pull off the top of the heater box to do the center vent & diverter pod, which is also a pain. This car (with 155kmi) had 4 bad pods: center vent, diverter, recirc (small lift), and defrost (small lift). Needless to say the system was NOT functioning as intended, although the ONLY symptom was a lack of air from the center vents with the A/C on. W124's are sneaky that way. ;)

So, I've said it before and I'll say it again: If you own a W124, particularly one that's older or with high miles, you should check the operation of the pods to make sure your ACC is working as designed! It's easy to test. Pull the glovebox and the 7-port manifold is right there on the left side, attached to the heater box. Remove one hose at a time and connect a MityVac. Each hose should hold vacuum. If not, the rubber diaphragm for that pod is torn. You can identify the function from the ACC service manual, if you want to know what's not working (assuming it's not obvious). The pods from Rusty (or FastLane, etc) are ~$15-20 each for the single chamber ones (center vent, floor, and diverter), and $25-30 each for the dual chamber (both recirc and defrost). I've heard that George Murphy sells a diaphragm kit to repair the pods but I don't know details or pricing, or how hard it is to repair them.

It took me 2 hours to remove the dash, 1.5 hours to replace the 5 upper pods (I left the footwell pod alone), and 2 hours to reinstall the dash. Total was 5.5 hours. If you do this, I HIGHLY recommend replacing ALL the pods that require dash removal!!! This is NOT a job you want to repeat a few months down the road when the next old one fails. Change 'em all and then you don't need to worry about it for the next 10 years or 200kmi. The two exceptions are the ones that don't require dash removal; the defrost & footwell pods. These can be done at any time in 30-60 minutes.

Tips for installing: Leave the flat metal bars attached for the recirc pods. Undo the connector tabs at the pod and reconnect to the new pod. Most of the pods have a lock tab that must be pressed before they will rotate out (I learned that the hard way last time - don't ask.) The diverter pod is held in by 3 round metal press clips, so you need to break out the old one and save the mounting clips for the new pod. The center vent pod is the trickiest. Although the manuals says you need to pull the heater core (YUCK!) it is not necessary. Remove the white pin in the top door. Remove the door by flexing it out of it's hinges. Remove the flat metal rod from the pod. Pull the hose and twist the pod out, it will *just* wiggle out from under the mounting bracket. Oh yeah - just before you reinstall the dash, do the MityVac test one last time on all 7 hoses! Otherwise, if you forgot to connect a hose you need to repeat the 4 hour dash R&R job! (Oh, joy!)


For the record, of the three 1987 300D's I've tested, this is what I found:
=======================================================
Car 1 (155kmi) - bad center vent, diverter, recirc, and defrost
Car 2 (229kmi) - bad center vent, recirc, and footwell
Car 3 (238kmi) - bad diverter, recirc, and defrost


And a couple more 124's I've tested since the original post:
============================================
Car 4 (86 300E, 200kmi) - bad center vent, diverter, recirc, and footwell
Car 5 (87 300E, 110kmi) - bad center vent, recirc, and defrost



Part number list:
======================================================
124-800-00-75 = Defroster pod (dual chamber)
124-800-02-75 = Center vent pod (single chamber, twist-on)
124-800-03-75 = Diverter pod (single chamber, small, attaches w/3 clips)
124-800-04-75 = Recirculation / fresh air pod 1 (dual chamber)
124-800-11-75 = Recirculation / fresh air pod 2 (dual chamber)

124-800-01-75 = Footwell pod (round, small, to VIN A289309, 1986 to early 1987, two required)
124-800-09-75 = Footwell pod (rectangle, from VIN A289310, late 87 through 95, one required)


NOTE: Of the pods above, only the -02-75 (center vent) can be properly "rebuilt" using the diaphragm kits from Performance Analysis. The dual-chamber pods can only have the 'small lift' portion rebuilt properly. The diaphragm kits for the dual-chamber 'large lift' will restrict movement and should NOT be used... replace the recirc+defrost pods with new pods only! There are no rebuild diaphragms available of any kind (good OR bad) for the small round pods (diverter and early footwell), nor for the rectangle pods (late footwell).

Photos are at this URL:
http://www.w124performance.com/images/W124_dash/


Do yourself a favor - grab your MityVac, pull the glovebox, and check them out! Summer's coming up fast and a fully working ACC is a beautiful thing.


:D :D :D


Best regards,

Dave:

I recently acquired a 1989 300E with 127,000 miles. The blower fan never seemed to go on high, but knocked softly instead. The knocking has stopped, but no high fan. I've been investigating that problem and today pulled the glovebox to see what I could see. I noticed that the pod behind the glovebox (you said it is for the defrost) does not activate unless I push the metal connector in a bit. Once in (when on a/c or economy) it will go back up as long as I do not let it go out completely (i.e. by putting the system on defrost, bi-level or off). Once all the way out, it will not go back in. Think this is a vacuum problem?

Hi Jim,

That sounds odd. I'd test the actuator first, using the procedure described above (apply vacuum to both ports on the pod). Use a Mity-Vac if you have one, if not, use the source line into the top of the 7-way manifold with the engine running.
Note: With vacuum applied to one of the two ports, it will move a LOT. When applied to the other port, the movement is almost invisible. You can see it if you watch closely though. With a MityVac (the kind with a gauge on it), you want to make sure both hold ~25 inches vacuum. If the diaphragm is torn it won't hold any - dead zero, usually.

If your pod checks out, it's either something with the vacuum plumbing (not likely), or an electrical gremlin (more likely).


HTH,

Does anyone know what the diverter flap is used for? I pulled my glovebox today, and tested all the vacuum pods - this one and the recirc small lift are bad.

Symptoms are no air through center vents (center vent pod holds vacuum, but I can't hear any flap actuation), and low air volume - high blower sounds like high blower, but only puts out min blower air.

When I applied vacuum to the diverter pod, it wouldn't hold a vacuum unless I quickly applied more than 10" Hg, then it held, but slowly leaked. With the engine/fan on, I got lots of air through the center vents, but little through the side vents.

any ideas?

-anthony

p.s. Thanks for an excellent post, I've referred to it often enough that it gets bookmarked..!

Hi Anthony,

Wow, that does sound odd. The diverter flap, from what I understand, allows a different airflow path through the internal coils. I'm not sure what the exact function is. I do know that if your center vent pod is dead, you can switch the signal to the diverter pod (if it's good) and get air out the center vents, otherwise your AC operation is poor with no center vent airflow. The side vents are fully open at all times with no flaps controlling them. If airflow is poor there, you either have a blockage, or the end vane piece (what you angle & adjust with your fingers) is not installed into the duct properly.

About the center vent, it will only blow cold air... with the heater on nothing comes out there. When you apply vacuum, you should be able to look through the center vent opening with a flashlight and see the "floor" drop away, revealing the AC evaporator (just barely visible). If you see no movement, your center vent pod is either dead or disconnected internally, or perhaps has a pinched/blocked hose?

Either way, if you plan to keep the car for a long time, I'd yank the dash and change them all. George Murphy sells rebuild kits which claim to work on single & dual chamber, however they do NOT work properly with dual-chamber pods. And the diverter pod is a different size, as is the footwell flap pod(s). That means of all the pods in a 124 dash, his kit works for the center vent pod only! Rather than mess with those, just get new pods for everything. I'm going to be doing my other 300D this winter (one of the 3 cars mentioned originally), and I'll be taking photos this time to document the process...

:D :D

Regards,

Alright, well I figured out why I wasn't getting much volume through the air vents: the blower fan was installed wrong! (boy, do I hate doing the same job twice. At least it only took me two hours instead of eight...)

I still haven't figured out what the diverter flap is for, from the shop manual it looks like it only opens when the system is on 100% recirc, and lets a greater volume of air through the center vents, but it's closed on any other setting. Since I don't get any air through the center vents period, I think the diverter pod is dead, and the center pod must be disconnected (or otherwise broke) somehow.

I tried looking through the center vvents to see if I could detect any actuation of the center pod, but there's another flap in the way (the one connected to the thumbwheel on the vent itself).

Thanks for your help so far - if you do get pictures (!!!) on the dash removal, I bet a lot of people would love to see them. I know I will. :)

-anthony

Hi again - I did my other car this weekend (third time I've done this job now.) Photos are at this URL. It took me 1 hour to remove the dash this time! I don't think it could be done any faster though... still takes 1.5 hours to replace the pods, and 1-2 hours to reassemble. Anyway:

http://www.w124performance.com/images/W124_dash/

Enjoy!

I'll upload a couple that are small enough to get through the forum size limit, for those of you too lazy to click the link. :)

Here's a shot of the center vent pod, buried in the heater box, in front of the heater core:

And here's proof that it can be removed through the top door, without pulling the heater core like the manual says. Small hands are required, if yours don't fit, find a helpful small child and bribe them with lollipops or something: :D

Here's a photo of the innards. One obviously has lots of holes and is all torn up. The other one had hairline cracks near the wide bottom end, almost invisible until you start pulling on the rubber and find out it's not all one piece any more! :eek:

Just a quick update to my original post (which I have edited). The vacuum pod rebuild kits sold by Performance Analysis company work on single-chamber, large size pods only. That means for the 124 it will rebuild the center vent pod and that's it. On a 123, same deal, center vent pod only (possibly the footwell flap, I'm not sure). The 124 diverter pod is smaller, and the older 124's have a rectangular footwell pod.

For the dual-chamber pods, the rebuild kit will fix the forward (small lift) section only. The rear (large lift) section is non-rebuildable! The kit has an interesting way to get around that, and it looks great, but DOES NOT WORK. It looks like it works, but when you apply vacuum and measure the rod travel on a new one (or good used one), compare that to the freshly rebuilt pod. The rebuild simply does not have as much travel. It all makes sense when you see it, but it's very hard to describe. That means if you use the rebuild kit, your pod won't fully open the flap it's connected to! And considering the amount of work needed to pull the dash & replace these things, you don't want to screw around. Buy NEW pods - for EVERYTHING - and replace them all at once. Believe me, it's worth it, and having the system work as intended is a beautiful thing!


Best regards,

Evaporator core replacement X's 2
 

Hello Dave,
Have you ventured into doing the evap.core on the W124's. I need to do this on both my cars. I am very mechanically proficient but need a little nudge as i am afraid of the unknown. How bad is this job. Can you walk me through it very high level...or just how to remove the dash. I have a MB tech that works on the side that supposed to be coming by this weekend to do both cars... Just R/R dash and Evap cores x 2. If I could already have the dash out I could save major dinero. If you say I almost home after removing the dash, then i may not even bother calling him. Please let me know. if its not too much of a bother, perhaps i could call and speak briefly with you and get the particulars if I have ?? with your brief outline. Thanks in advance

Hi Albert,

I've never done the evap or heater core. I think you have to pull the heater core out to access the evap - not fun. Pulling the dash is not too bad, just tedious. THe procedure is in the factory manual, it's pretty basic. You will have a LOT of little parts, so have a workbench are or some place you can set each item & the screws for it separately. And it should be somewhere that it can stay apart for several days if required! Definitely replace ALL the vac pods while the dash is out, particularly the center vent pod. Photo of the heater box is here:

http://www.meimann.com/images/mercedes/W124_dash/top_removed.jpg


More photos:
http://www.meimann.com/images/mercedes/W124_dash/


Note that the pipes leading into the evap are also hard to get to, at the expansion valve, under the windshield trim , behind the brake booster. It's definitely a major procedure. I think you could do the dash removal yourself, if you follow the factory procedure carefully. Acutally pulling the core & evap is what I don't know about - I'd ask your friend and see what he says! Just curious, are you *sure* both evaps are bad? Maybe it's just a failed O-ring at the expansion valve? I don't often hear of evap failures on the 124 chassis...



Regards,

Hey GSXR

I looked at your 350SD head replacement pics. Very impressive. Just for future reference, what is the part number for the new head? If I decide tog et one of those beastly engines, how will I be able to tell if the work has been done?

Regards

GXSR,
Nice pix !! Any ideas how I might clean mold/mildew out of my '82 300SD 126 core without taking the dash off to get to it? Everything I read says the core is buried too deep for casual access. I've taken off my blower motor and cleaned it out, but as the humidity of summer approaches, I can smell the mildew when the ACC is on. Any thoughts would be appreciated!

-----------------------------
Steve Kaa

1982 300SD (312k):confused:

Hi guys, thanks for the complements! ;)

Warren - the part number you'd order from the dealer is different than what's cast into the head. Look on the head, above the #2 and #3 injectors. You will see a number that is something like 603-016-xx-01. Only the 7th and 8th digits are important. If "xx" is number 15 or lower, it is the old head that is prone to cracking. If the number is 17 or higher, it is the updated head which is pretty close to crack-proof, at least I haven't heard of one failing (yet). Number 17 is what should be on all 3.5L engines. The latest version, what you would get new for ~$1800, is number 22 I think. The heads with the problem were on 1986/87 300SDL, 300D, and 300TD's (all 3.0L). Mine is the 300D. All the 350SDL's and S350's had good heads, but bad connecting rods - different story there. :)


Steve - I'm not 100% sure. I believe if you check out some A/C supply places, you can buy a can of spray that's designed to clean the evaporator. Normall you pull the blower motor out, or something, so you can get as close as possible to the evap to spray it in (follow directions on the can). I have never done this on my cars though (but I need to on one of them). So I don't know if this will work for you or not, but it's worth a try!



Best regards,

OK, GSXR, now I'm confused. I have read about the bent 350SD conn rods. I have also read that it was caused by cracks in the cyl head letting coolant into cyl 1 and causing a hydrostatic lock, ergo a bent conn rod. I have also read about the expensive re-engineering done to the engine. Is this incorrect? What is the correct story on rough running 350SD's?

Thanks a bunch

Warren, the bent rods are correct, but the cause is not the cylinder head. The 3.5L heads are great. The cause appears to be weak connecting rods. There was no major engine re-design, just new rods, AFAIK. There was a great page on MBZ.org with this info but it's now gone, possibly lost in the server crash last fall. Here's what I dug out of my archives. Also search the ShopForum archives:

From: alt.auto.mercedes #46707
NEWSLETTER: 3.5 Liter Turbodiesel
Posting-Date: 6 Jul 1999 19:33:14 GMT

INTRODUCTION

This newsletter is being made available via the world wide web to all those
interested in the problems with the 3.5 liter turbodiesel engine used in
S-Class Mercedes between 1990 and 1995. It incorporates significant new
research and information and the input of several list members since my last
communication some time ago.

Briefly, this engine has problems. With distressing frequency these engines
show significant, grossly premature wear, requiring expensive rebuilding.
Symptoms are excessive oil consumption, mechanical noise, smoke, and a
throbbing idle. Diagnostic procedures usually reveal that one or more
cylinders have compression that is below specification, with excessive
variation in the compression among all cylinders. Mechanical teardown
frequently reveals cylinders that are out of round and connecting rods that
are bent. Catastrophic engine failure has occurred quite often. These
problems are clearly due to a design defect that Mercedes refuses to
acknowledge. These problems can not be prevented with any sort of routine
maintenance, nor can they be forestalled with changes in driving behavior.
In essence, the engine self-destructs during normal operation. Symptoms have
appeared as early as 50,000 miles. Due to the expense of individual
repairs, Mercedes honors warranty repairs only after considerable pressure
is applied. Out-of-warranty claims are summarily rejected.

The newsletter can be downloaded at: http://home.att.net/~thcg/mbnl.pdf
(this link is dead now. Anybody have a new one ?)


(this is an Adobe Acrobat file and you will need Acrobat to read the
newsletter)

Copyright 1999 John A. Blazer. May be liberally quoted or copied, provided
attribution is given.


This is the first substantive bulletin to those interested in this engine.
Hopefully the mailing list is relatively clean. If you know of someone that
should be added, please advise.

Why this Group? Because this engine contains a design defect. It
demonstrates significant wear quite early. It is expensive to repair.
Mercedes will disclaim responsibility whenever possible.

Which Cars? S-Class TurboDiesel Mercedes model years 1990 through 1995.
Includes W-126 with engine 603.970 (1990 350SDL, 1991 350SD, 1991 350SDL)
and W-140 with engine 603.971 (1992 300SD, 1993 300SD, 1994 S350, 1995
S350.)

Symptoms? The most common symptom is excessive oil consumption - 1 quart in
as few as 100 miles is not unheard of. Other symptoms include throbbing
idle, smoke, mechanical noise. Many owners report an episode of the engine
'bogging down,' 'grunting,' or similar such description, followed by a puff
of smoke.

Diagnostic Steps? Monitor oil consumption very carefully. Opinions vary on
what is 'normal,' but certainly an increase in consumption needs to be
investigated. Most people consider 1 quart per 1,000 miles to be acceptable;
1 quart per 500 miles is probably not.

Next step is a compression test. A wet and dry leakage test will help
determine whether problems are related to rings, or to valves. Engine warm,
all injectors removed. Design specifications call for compression of x-x
psi, with a range between highest and lowest of no more than x.x psi.
(Source: )

Assuming further investigation is indicated, the head will be removed. May
reveal carbon buildup in combustion chamber; worn valve guides or seals;
scored cylinder walls. Most critical: deck height, i.e., whether all pistons
rise to the same level. Differences indicate bent connecting rods and/or
pistons. Further disassembly may reveal worn or broken rings, deformed
pistons and/or out-of-round cylinders.

------------------------------

Dave, super write up and pictures on your site for those with ACC problems on the w124's. Sounds like there most likely will be problems developing with some of these pods on the majority of cars with more than 100+k miles.

I'm wondering if access to the 7-port manifold for testing of good holding vacuum for each pod is dependent on the car NOT having a passenger side airbag? In other words, you seem to indicate that the 7-port manifold is somewhere behind/below the glove box area. So does having the passenger air bag make any difference in being able to do your recommended test ?

Hi JD,

Oooo! Good point. I believe the 7-port manifold is located in the same spot, but the airbag resides in the usual glove box area. I'm not sure if you'd need to pull the passenger airbag to test the lines, or if you could pull the lower (interior colored) trim panel & still access them. If someone does this, let us know for future reference... :)


Thanks!

ACC Actuator vacuum pod repairs
 

This thread on 124 series ACC repairs is very useful.

With some great advice from George Murphy of Performance Analysis, I've gotten far enough into diagnosing my own ACC system on a 124 series 1988 300TE to determine that the defroster actuator #38, the center nozzle flap # 40 and the two for fresh/recirculated air #42 are all leaking.

I have a couple of questions on this topic.

Anybody have any experience with ACC Actuator repair kits from Autolux? www.autoluxmbz.com

I'm concerned that their kits may result in the same limited motion Dave describes as a drawback to the actuator rebuild diaghragm kits sold by Performance Analysis.

Here's where I need some strategic advice from you folks who have been down this road. This car has 193Kmi and needs plenty of other work, my budget is tight and my time limited. I'm looking to get two more years out of it for daughter #2 to drive to college.

If I replace only the easy one - the defroster actuator #38 can be reached through the glove box opening, will I get any improvement in operation?

How do the various circuits default with no vacuum?

I never bother with the recirculator switch, so that's not really essential unless as I suspect, the ACC unit uses it to optimize speedy cool down or warm up depending on outside temp. Similarly, we can probably live with cold air coming out the side vents only and skip replacing the center vent actuator #40.

If I go this route, should I cap the now abandoned circuits at the vacuum block?

Thanks for any and all advice.

Jerry Murphy

'88 300TE
'97 E420
'97 Audi A6Q wagon
'67 Morgan +4
'37 Cadillac 7553 V8 Fleetwood Town Car

Hi Jerry,

The Autolux kits are the same as PA's - don't use them. Buy new pods from your favorite e-tailer (FastLane, Rusty, EPS Parts, etc). The system defaults to full defrost with zero vacuum signal. Replacing the defrost pod will allow the defrost vents to fully close and prevent cool air from going to the windshield in the summer. I'd definitely replace that one if it's bad. And you can live with the recirc pods, as mentioned. A band-aid fix for the center vents is to swap signal lines on the diverter and center vent pods. A signal from the center vent port, when directed to the diverter pod, will allow cool air out the center vents. It's not the "proper" airflow pattern inside the box but hey, it will limp the system along until you can yank the dash and fix them all correctly. And no, you don't need to cap off bad circuits, I think the manifold has built in restrictors that prevent any leaks from causing other pods to not work.

:)

HTH,

I have a 92 300E. Where the glove box should be there is an airbag instead. Is there I glove box I don't know about?

While I'm getting this job done, and the whole dash apart, is there anything else that I should have changed while I'm at it ? it's for my 87 260E.
I've heard of the A/C related item, evaporator I guess that sits behind the dash. I'm not sure if it was the evaporator, but something A/C related... what else should be changed while the dash is open ?
thanks guys.

Does anyone know if the climate control vacuum manifold can go TU on the 124's? The footwell vents on my '87 300 td won't open unless I use my mityvac directly on the vacuum pod. The defrost pod works fine and is actuated by the pushbutton unit.

Is there a way to diagnose why my footwell vents don't operate correctly, and is this most likely a failed pushbutton unit? It's been rebuilt by the PO at some point.

BTW: Thanks for the great pics Dave--I find your website very helpful for us 124 owners.

Thanks

So far, I haven't heard of a bad 7-port manifold. Usually it's the pushbutton unit failing to provide the proper signal. But, there's always a first time! Perhaps check in the factory CD-ROM service manual, in the ACC section, there is some good troubleshooting info in there. If all 7 of your lines hold vacuum, consider yourself lucky - for now! ;)

Benz300,

Ooops! I missed your post. While the dash is out, replace ALL and I mean EVERY ONE of the climate control vacuum pods with new ones from FastLane or Rusty. Replacing the evaporator is an even more extensive job, and while 124 evaps are prone to failure, I would not change one out that was good and showed no evidence of possible failure. It is NOT cheap and NOT fun to do. And, you'd need complete A/C tools to evacuate the system, pull vacuum afterwards, and recharge. It's worse if you have a R-134a system, as you need to work fast and get the system sealed & under vacuum ASAP, since the PAG/POE oils soak moisture out of the atmosphere rapidly when the system is open. This isn't a big deal for R-12 systems with mineral oil, but those are becoming more rare (sadly). Bottom line, do all the vac pods, and replace any brittle vac tubing & rubber fittings (they're usually OK though).

:D :D

gsxr:

Was your center pod hooked up and working right? I've just extracted mine out of the heater box, and was a little surprised to find it ... not hooked up at all. There's a short length of hose running off the center hookup on the switchover valve, but it's capped off. Wondering if it came from the factory like this ('87) or if it was a quickie fix for something else somewhere down the line.

No, that's not normal, it should all be connected. Sounds to me like it was leaking and someone capped it off to prevent the leak from affecting other pods. Test everything with a MityVac, replace the leaking pods, and connect up all the hoses...

:)

Hi Dave.

Thanks for your posting on the vacuum pod replacement, and especially the clues about Y7 being in the glove box. The pictures from the CD are so poor that it is not possible to see that they are inside the dash.

After spending a day and a half digging around my ACC to see what the problem was, I've decided that most if not all of the pods are indeed bad. I'll be ordering some sooon.

I wonder if you have references to the 124 manual procedures for removing the dash. I'm not looking forward to it as I don't have much experience with this level of repair. I figure if I can review the factory procedure I might be better off.

Sean

Sean, the factory manual on CD has the procedure for dash removal. That requires several "sub procedures", which are referenced so you can look them up. It's not really hard, just tedious - plan on a full weekend and be happy if it goes faster. Buy all new pods before you start - yes, even replace the "good" ones because they won't last much longer anyway! Also you'll need a pretty large working area as you'll be removing a lot of parts that need to be carefully laid out, so you can remember how to put it back together. A digital camera, or Polaroid, will help if your memory isn't good. Fully extend the steering wheel before starting, and be *super* careful not to break the cruise control switch stalk when stuffing the dash back in place - trust me, it's annoyingly easy to break...!

:)

(bump)
 

Summer's here.. somewhat, might as well bump this and let everyone troubleshoot their ACC system.


Dave, do you have the part numbers or what all the different pods are called? I tested my system today, only the footwell and the one nearest to the 7-port manifold works (what a suprise... :rolleyes:). Anyways, I'll probably do it next weekend if i can round up the parts. I already have my center console removed so that I can fix my auxillary power outlet's cable (cigarette lighter). Until I can get the parts.. i think my center console is going to remain like this for a while

I can dig up the part number if you'd like... :)

Please, if possible :D

124-800-00-75 - Defroster flap control
124-800-02-75 - Center vent air flap control
124-800-03-75 - Cold air flap control (diverter)
124-800-04-75 - Main air flap control (Left)
124-800-11-75 - Main air flap control (Right)

124-800-01-75 - Footwell flap control (Round, 2 required) - Up to VIN 289309
OR
124-800-09-75 - Footwell flap control (Rectangle, 1 required) - From VIN 289310


Numbers 00, 04, and 11 are "dual chamber" pods. Numbers 01, 02, 03, and 09 are "single chamber". All of 6 them will be ~$150 new. Note that later 124 chassis with the dust filter use different part numbers for all three dual-chamber pods. The numbers listed above are for cars without the dust filter (pre-1990).



:cool:

gsxr,

It seems that you know quite a bit about changing the vacuum pods in the dash.

I have a problem on my 1987 300TD in that air doesn't come out of the floor vents when the heater is on. It seems that the hot air comes out of the defroster vents.

I popped out the glove box, and I checked all of the vacuum pod hoses with my Mity Vac pump (as mentioned in this post) and only one line seems to not hold vacuum. It is a red hose with a black stripe connected to the manifold on the #4 port. I don't have a schematic diagram, but I am assuming that it is the vacuum pod that controls the footwell flap. According to your post, the footwell flap pod can be changed out by removing the climate control on the center console.

What is the procedure for taking the climate control out to change the vacuum pod behind it? I haven't found any info on how to take the console apart to get the footwell flap pod out when I did a search. Any help would be appreciated. (I only found info on how to take out center console with the window switches.)

BTW, the post on the vacuum pod testing was very helpful.

Thanks in advance.

-Steve

Steve,

It sounds like you may have a vacuum leak somewhere. Port #4 with the red/black tube goes to the center vent nozzle. I bet you never get any air out the center vents - you should get cool air (never warm air) when the temp wheel is set to cool. If you have no vacuum, the default airflow is full defrost. On heat, you should get a trickle out the defrosters, and full footwell air. On cool (or A/C), you should get nothing at all out the defrost or floor, but air out the dash side & center vents. Check the green/yellow vacuum source tube at the top with the engine running and see if you have vacuum present. If not, you likely have a vacuum leak, or hose dislodged, in the engine compartment.

BTW - your failed #4 port is a bear to change, as noted in my post above! A band-aid fix is to swap #4 and #6, which at least gets cool air out the center vent at the proper time, just no with the correct airflow through the heater box.

:cool:

GSXR, thats different that what I am noticing.

I seem to get air out of the center vents when I set the ACC to any temperature lower than ambient. The center vents work for more than 15 minutes as well so it not a temporary thing. The only time I get air out of the footwell flaps is when I turn the temp on the ACC up to above ambient and then it is only for a few seconds that the air comes out of the footwell flap. It then starts flowing out of the defroster vents.

When I tested the lines they all seemed to hold 15" of vacuum except the one on port #4.

So what vacuum pods do each of the lines 1 through 7 go to?

I thought for sure the footwell flap pos was bad, but it looks like this may get interesting.

I'll check the vacuum on the green/yellow vacuum source tube as well.

-Steve

Strange! Port #4 goes to the center vent pod. However, you can still get air out the center vents with port #4 bad, if the diverter flap opens (#6). What you can also do is turn the fan on maximum and apply vacuum to one port at a time, and observe the difference in output at the various vents. I'm starting to suspect a flaky pushbutton unit as the cause of your floor vent problem though, but if #4 doesn't hold vacuum, your center vent pod is dead (or the line is disconnected, or leaking). All the diagnostic information is in the climate control service manual on the CD-ROM. If you need the CD, drop me an email.

Oh yeah - to remove the climate control unit, remove the two Phillips screws at the bottom of the wood trim, directly above the radio. Then carefully lift the wood off, pulling the bottom outward, and the top will unhook - no force needed. Then there are 4 or 6 screws holding the p/b unit in - remove those, it pulls straight out. You can see the footwell flaps from there and observe operation while applying vacuum.

:)

That's clever, swapping the diverter flap vacuum hose for the center vent vacuum fitting.

Dave - Any idea when these crazy cars decide to open the diverter flap? Mine does so on occasion; I can tell by the noise. But I have no idea what criteria the pushbutton unit uses to trigger that decision.

One of us should probably post a listing of the vacuum hose color coding, and the vacuum ports on the seven-port valve. I'd do it now, but I don't have the shop manual handy on this computer. Sounds like this guys car may have the hoses switched around.

- JimY

I checked and his #4 colors match. I am not sure when/why the diverter opens, or what the purpose is. The climate control manual does not explain that technicality very well. To me, it seems to force air through both the condenser AND heater core when close, but when open it may allow air to bypass the heater core (which sits in front of the condenser). That's a total guess though, and I don't understand how that would affect operation anyway under normal/max cooling (not bi-level).

Having pulled the heater box, it's fairly obvious what the diverter flap does, I just can't figure when or why it is used.

For the unititiated, in a 124 the air travels from the blower fan, through the a/c evaporator, then through the heater core, and finally into a plenum at the rear of the box (the part of the box immediately in front of the pushbutton unit). From the plenum there are several doors which can be opened or closed to direct airflow. There are doors for the footwells, the center vents, and the defroster ducts.

In addition, there is the diverter flap. It permits air to exit the heater box after passing through the a/c evaporator, but before passing through the heater core into the plenum. This "diverted" air exits only through the center vents.

Here's a thought. Maybe it's used for the Hi/Lo setting. Permits warmed air to be blown out the footwells while cooled air comes out the center vents. I'll dig up my CD over the weekend and take a look.

Returning from our thread hijacking, something is wierd with swogee's car. If #4 leaks, it should not be possible to get air out of the center vents. If the footwell flaps won't stay open, I would expect to see a leak in either the footwell flaps or the defroster element.

I'll try to post a listing of the tubing color codes and positions on the valve over the weekend.

- JimY

OK, here's a listing of the vacuum lines and vacuum block connections for the 124. The #1 connection is the top of the vacuum block, #7 is the bottom.

#1) Fresh air/Recirculated air flap small lift. Line color is dark red. When activated, this line moves the recirculated air flap from the 80% recirculated (i.e. mostly closed) position to the 100% recirculated (fully closed) position. With the glove box removed, you can actually see part of this flap, directly in front of the heater box, up against the firewall. This port on the vacuum block is activated with pushbutton "0" (i.e. off) pushed.

#2) Fresh air/Recirculated air flap large lift. Line color is medium green/light blue. When activated, this line moves the recirculated air flap from the open position to the 80% recirculated (mostly closed) position. With the glove box removed, you can actually see part of this flap, directly in front of the heater box, up against the firewall. This port on the vacuum block is activated with pushbutton 0 pushed.

#3) Footwell flaps. Line color is red/yellow. When activated, opens the flootwell flaps. This port is activated with the hilo pushbutton.

#4) Center dash vent flap. Line color is red/black. When activated, this line opens the center dash vents. The vacuum port is activated with the "EC" pushbutton selected and the temp wheel rotated to the min position.

#5) Defroster vents large lift. Line color is red/white. The defroster vents are normally fully open. When this line is activated, it closes the defoster vents most of the way, leaving a bit of air to leak out the defrost vents. The vacuum port is activated with the "EC" pushbutton selected and the temp wheel rotated to the min position.

#6) Diverter valve flap. Line color is medium green. See previous discussions in this thread for the function of the diverter flap. The diverter flap is normally closed, applying vacuum opens it. The vacuum port is activated with the EC pushbutton selected and the temp wheel rotated to the min position.

#7) Defroster vents small lift. Line color is red/light blue. This line takes the defroster vents from mostly closed (see #5 above) to completely closed. The vacuum port is activated with the "EC" pushbutton selected and the temp wheel rotated to the min position. On my car, it seems to leave this port unactivated for the first 30 seconds after starting the car, thus directing a little bit of air to the windshield. Then this one port is activated, completely closing the defrost vents.

- JimY

While my climate control system (87 300D) appears to function properly in all modes, can a bad pod, or more than one bad pod, cause a drop in vacuum to vital functions for the engine?:confused:

No. However the opposite is true - a loss of vacuum from the engine compartment (disconnected line, etc) can cause improper ACC function.

:cool:

gsr,

How do you take the vents on the dash out, without causing any damage. I am in the process of replacing my dashboard, and I do not break anything.

Thanks a lot,

Sam

There are four little metal spring clips that hold the vents in place. You gently pry up with a tiny screwdriver while wiggling the vent forward. It comes out a little bit at a time. The center vents also have a screw on one (or both?) sides, but I think the end vents just use the clips. They're a little annoying to remove. If you have to use force, you're probably doing something wrong - they should come out fairly easy.

BTW - if you are pulling the dash to replace it, it would be foolish to NOT replace all the vacuum pods - I assume you plan to do that while it's apart! :D


:cool:

I posted earlier in this post about the possibility of vacuum loss from the climate system effecting engine operations (thank you GSXR) and noted that my climate system worked properly but I was mistaken when I had to turn on the windshield defroster yesterday and got only hot, real hot defrost and I cannot seem to change it that much, even with the control nob turned to coldest.

You can hear the AC comp. come on and it does try to cool it down a bit but something is telling the heat to engage at full open.

Does anyone know what's up with my defrost? All other functions seem to be normal!

gsxr

Thank you very much. I will read your post, and see about the pods.

Thanks again.

Sam

Sooty - sounds like the monovalve is stuck on, or not getting the signal to turn the heat flow off? Might be hard to diagnose on a 124... this is not a common problem like it is on the 123 (which has a *totally* different monovalve setup). Could also be a bad pushbutton unit. :(

Sam - good idea - and good luck! ;)