Yep. It's supposed to blow only hot when the defrost selector is on with the A/C compressor engaged to dry it out. The defrost selector is ment for quickly defrosting the window like when you are just starting up. If you want cold air coming from the defrost vents hit the button next to the defrost selector. This will still vent air through the defrost vents but you can have cold air if the temp selector wheel is on cold setting.

Thanks for that reply Christophe.

While I do agree with you that heated air is mixed with AC/cold, nothing clears a fogged window faster, but this just began happening!

Before, the defrost used to come on only warm, or set by the thermostat temp setting, not scalding hot, as it is now! You can't use it on a warm day, it'll drive you right out of the car! I doubt MB would have it this way!:rolleyes:

I have a couple of things to add here. Replacement of the diverter pod (small black one on top of the heater box) and center vent pod require that you remove the top of the heater box. A magnetic pickup tool is a HUGE help - it's too easy to drop the small metal clips into the console, not to mention the two screws that are up against the firewall (a bit hard to see). The diverter pod is held in place by three press-fit washers, a poor design IMO. Use small diagonal cutters (dikes) or end cutters to get in under the washer and cut the plastic stems. To press the washers back onto the new pod, a small 1/4" drive socket works well.

Removal of the bracket holding the seatbelt warning relay (it's to the left of the left recirc pod) will make removing the pod a million times easier. Removal of the defroster pod makes it easier to remove the right recirc pod too.

Sooty
My '87 300TD has the same defrost you are describing. Hot as hot can be and you are correct in stating it will drive you out of the car. Mine is also showing a mind of its own when it comes to the compressor engaging. Sometimes it will other times it won't. I find the second to be the most annoying. POD replacement will be one of my late Fall's project.

As a note to GSXR comments,

I have a friend which went with the $5 diaphram replacements for his W124. He was/is *NOT* happy. They do fit... they do not leak but be warned the travel is not equivlent to the stock units.

If you can afford the OE parts, this is not the place to save money. Too much work !

Thanks for the p/n's . I double checked mine 5 minutes ago. I've got all the correct stuff and have planned out about 8 hrs today. If all goes well, we'll drive it to work tomorrow. If not... wife can take me=)



Michael

Thanks for the confirmation. :) The diaphragms will work properly for the single-diaphragm center vent pod, and the "small lift" portion of the dual pods. But for the "large lift" section of the dual pod, the movement is restricted to about half of normal travel!! I'm disgusted that George sells such a poorly designed, borderline defective, product. New pods are only about $30 each, and since they last 10-15 years, I think it's worth every penny. Plus if you break a plastic tab while rebuilding the old pods, you'll have to buy a new one anyway...!!

:p

Hey GXSR or anyone
 

1) I only get heat from the defrost function. I cant get heat from the two pushbutton functions to the right of the defrost function, I only get ice cold AC. No matter what range I spin the Climate Control knob, its cold stuff.
Is this a problem with the push button unit circuit card or one of the diaphragm pods?

2) Does anyone have experience with the Central Locking Vacuum Pump underneath the rear pass seat on the pass side of car? I cant get the A, B, or C 10V signal by locking/unlocking at the 3 main positions and it may be because this signal is routed through the oboard alarm which ihave disconnected. Can I use engine vacuum instaed?

1) That's definitely not vacuum related - you have an electrical problem of some sort. Could be the pushbutton unit, or a faulty temp sensor - you'll have to use the ACC manual to troubleshoot.

2) No clue on the door lock pump. You can't use engine vacuum though. Or at least that would be a bad idea. The older cars had a big vacuum reservoir in the trunk for the door locks, the 124 doesn't have that. It should not be tied to the alarm in any way. I disabled my alarm too (yanked the Becker brain box out from under the front passenger footwell). Used pumps should be cheap, but a new pump is stupidly expensive, if the pump is bad. I'm not sure what the problem is there either...! Now if you have an aftermarket alarm installed, you need to figure out what the installer screwed up!!!

:o

Updated original post and fixed the link to the photos. Bump for new members. I'll post the list of part numbers too... stay tooned.

:)

Added part number list to first post. Enjoy!

:D

Alright, I have my father's 1987 300D turbo to be restored soon. Well obviously I havent touched the car in a long time. But ive noticed the climate control does not work properly. I only get air out of the defrost mode. I press center vents , floor or economy and the air only comes out thru the defrost and side vents. I also think the temp dial is not working eiether. Is this a electrical problem or some sort of vacume situation.

Though my '87 was not suffering from no air flow from the center vents as you are indicating you are facing, a couple of forum members gave me great advice. Vacuum is so important to these systems. Do you have a miti-vac to test some of the components? If not, get one. How about manuals? After reading the threads pertaining to the automatic climate control, I purchased the MB Service Manual Automatic Climate Control Model 124. It covers everything. So, are you yet armed with the above?
Steve

If you ONLY get air out the defrost and end vents, you have a vacuum problem. Could be in the engine comapartment, you'll need to test. If the temp is wrong, that's probably electrical.

:)

I think the temperature is working fine now. I just didnt think it was regulating temperature correctly. I think I have a huge vacumm problem. The rpm gauge does not work eiether, i think that might be a vacumm also. Where should i start?

Vacuum problems are pretty common when the car gets that old. Time to start troubleshooting.

The tach (RPM gauge) not working is NOT vacuum related, it's electrical, and not likely related to your ACC issues. However, with the tach dead, your A/C compressor won't turn on at all - it's part of a safety circuit. First check the fuses. (It's actually a good idea to replace ALL the fuses every 5 years or so - some may fall apart when you take the old ones out.) Anyway, the dead tach is most likely a bad sensor, about $50 or so last time I checked. It bolts into the engine right below the starter, and the wire goes up by the oil filter and then behind the battery. Splice the new sensor in near the battery after routing the wire up there. You can test the old one with a volt meter, but you need to cut the wires open to get the probes on there... should read increasing AC voltage (not DC!) as RPM increases. Could be a bad gauge pod (in the dash) but that's not very common.

BTW - if you're new to the world of 1987 300D's, I'd suggest reading this little buyer's guide... it has some interesting tidbits you might like to know:
http://www.w124performance.com/docs/mb/articles/124.1x3_buying_tips.txt

:o

sorry if I missed it (this is a long post) but does the front footwell pod controll the rear footwell vent as well?

Yep.

:dj:

Thank you SIR!
:musicband

And another question. Do you think I can jam them open (carefully pry) from the outside -- with a dowel or something -- until I have the time and parts to fix?

Little heat to feet, all else o.k.
 

GSXR, I've got an '86 300E w/only weak airflow to the front footwells, I assume they are not opening up. As far as I can tell, everything else in its ACC functions as it's supposed to. Turning the fan up higher will give noticeably more air to the side vents if they're opened, or to the windshield, if side vents are closed. I think the rear seat floor vents are getting (somewhat) more airflow than the front footwells...

I did check the center vents btw, they get strong airflow when A/C is turned to Min. But my feet are Cold driving this car w/the heat on- what's the likely culprit here?

I also wondered the same thing as David, above, if the footwell vents can just be forced open easily in the meantime, for the winter months.

In case this means anything, my fan speed pushbuttons do not always work right when first starting out in cold weather, then they "loosen up" as things warm up and function normally.

MustMakeAmends,

With the heater on max, you should get minimal airflow to the windshield - just a trickle. You should get air out the end vents and the footwell. If the defroster pod is bad, the defroster flaps won't close and you'll get weak airflow out the footwell. If the defroster is ok, then you may have a bad footwell pod that's only partially opening. (??) It's not hard to test or replace the pods, you really should pop out the glovebox and test all 7 vacuum lines. If the footwell or defroster pods are bad, they're easy to change. It's the other 4 that require dash removal.

Side note: Your 1986 model has two small round footwell pods... later cars (mid-1987 up) have a single square pod. If one is bad, you may get little to no airflow out either side. My 1986 300E had one bad pod, which caused similar problems to what you describe. I replaced it and the footwell vents work normally now with decent airflow.

:cool:

removing glove box
 

I get fresh air with the system off so I must have a diaphram problem. The first step is to pull the glove box. I removed all the plastic push rivets-only broke one! Then removed the door latch on the roof of the glove box. I thought the glove box should come out. Does the light hold it in? I would hate to break the light /lens. Is there a trick to getting the box out? Thanks

Eric,

The light doesn't hold it in, but you will want to pry it loose and pull it down until you can unplug the connector then it will be out of your way.

Once all plastic fasteners are loose and the light is out of the way, you sort of have to collapse the box a little to get it to pull out.

I wish I were closer or coming to the Metroplex for some reason and I would give you a hand with it.

Hope this helps,

Yep, what Larry said. I pry the light down in front, then pull it out and disconnect the wire. With the rivets out, and metal latch unscrewed, just squeeze the middle of the box together and it will pull out. It's not terribly fragile, don't worry too much about hurting it. You can only replace the defroster pod via the glovebox opening, but you can test all 7 ports with the glovebox out of the way.

:o

I am at the beginning stages of DIY, I think ill try to tackle the AC issue while leaving the mechanical work to someone else until I get more familiarized with the car

Where can i get this tool mentioned in the beginning of the post? [Mity Vac]

My situation for my 300E 89 203k:
Purchased car w/ 103k miles, sometime after...
- cool air / hot air and defroster working fine
- cool air working but speed switches H/L/auto no longer seemed to make a diff / hot air working / defroster working
- cool air started diminishing / hot air working / defroster working
- no cool air / hot air working / defroster working

noticed that the car windows would sometimes fog from within the car when we went to the store, etc. That was during heavy raining season, not sure if it was related to AC or different issue (no longer does that).

- car battery dead / replaced car battery
- blower no longer works (not sure if blower went out before the battery was replaced and I didnt notice or perhaps I sorted something while changing the battery).

checked metal fuse outside of fuse box (appears to be original, do not see any cracks, perhaps i should change it anyways)

In one of the pictures I saw that there seems to be a fuse in one little box next to the rest of the components behind the battery, what is that fuse for?
http://www.davebarnhart.com/mb300e/Blower/images_fullsize/Wiper1.jpg

Had the dealer test the AC when the car was serviced, they mentioned that the climate control unit was currently working but not the blower, and would need to take it apart.

Figured the first thing I need to do is replace the blower after I figure out what all (if more than one) fuses i need to check, but would like to check the pods mentioned as well, so i can start to plan out what all i may need to do.

Thanks

That blue fuse is on top of the OVP relay to protect the electronics.

Replace the fan and if you go to the effort of doing pods- a good weekend. Do them all with factory parts- I'm hoping on mine that will mean another 15 years of trouble free service.

Michael

You might have a bad blower motor... they are known to eat brushes and need replacement by about 20 years or 200kmi. Less likely is the speed controller (aka 'porcupine') mounted under the fan, or the pushbutton unit.

The vacuum pods only control *where* the airflow comes out, not the temperature or fan speed.

:)

GSXR

Is there a step by step to take out the dashboard? Im in the process of taking out the dashboard to fix the vacuum problems I'm having. Im only getting air out of the defrost mod. I have a 1987 W124 300D TURBO.

Working around the climate control diaphragms
 

The '87 w124's have no passenger side airbags, so access to the ACC vacuum distribution block and the defroster's diaphragm is quite easy, by removing the glove box. Use a vacuum hand pump to diagnose open circuits. (an inexpensive and quite valuable tool to own!)

Elsewhere on this thread you'll see a link to a vacuum schematic and diagnostic steps for every possible setting. Take your time and write down your results.

I found that replacing just the defroster diaphragm and re-routing the center ones to the floor was quite effective in restoring usable function to the ACC system, albeit cheating a little. I capped off a couple of vacuum circuits that I abandoned. You can order the new diaphragms right from the shop forum sponsors - great value! Don't bother with rebuild kits - get new ones.

Removing the entire dash was more than I wanted to get into, so I simply abandoned the broken flap actuators that were difficult to access.

I drove my 1988 W124 wagon happily for another two or three years in this mode before selling it last year at 220K miles. Should have kept it. I loved that car.

Something to appreciate is the clever strategy of the engineers of this ACC system. The default of a total vacuum failure is to route all air to the defrosters - a good bet in cold climates! The default failure of the defroster control flap is to leave it wide open. You can still operate the car with a clear windshield even if your toes are cold, or hot.

Keep that nice car rolling!

Jerry

1) If the ONLY airflow you ever get is out the defroster and the end dash vents, that's a symptom of zero vacuum present... check for vacuum at the top of the 7-port manifold (with the engine running!). If there's no vaccum, none of the flaps will work.

2) As Jerry said, you can jury-rig things to make it a little better, if you don't have time to pull the dash. I swapped the center vent with the diverter pod to get cool air out the center dash vents... drove like this for 2 years before I finally pulled the dash and replaced everything (don't just change the bad ones, change them ALL.)

3) DO NOT get the rebuild kits - pretty sure I explained why earlier in this thread. Get NEW pods.

4) To pull the dash, you need the factory service manual procedure... Group 68, job 100. Here's a link to the PDF file online (3MB download) :
http://mercedes.braingears.com/124_DISC2/Program/Chassis/68-100.pdf

:book:

vacuum pods done, on to rest of ac system
 

gsxr - great tutorial on pod replacement. It was tedious & frustrating (6 hours) but my vents are now all blowing properly. 4 pods were bad. I have a few additional questions that relate to my goal of having a properly functioning ac system.

1. How can I tell if my evaporator is bad? I don't want to reassemble the dash if it's bad.
2. How do I test for no freon leaks on my 134 ac system? Can I use my trusted Might Vac? I've got to replace the receiver / drier (INDY shop charged system a year ago I told me that's why it gets cool but not cold) because it's not blowing cold & thus replace freon but I wanted to test for leaks prior to removing rec./drier.
3. I can spin the front wheel of the compressor so I'm assuming it's good. Can I add compressor oil without removing the compressor? How do you know if the compressor is engaging.
4. Should I go ahead & replace the expansion valve also? I think it's the original but not sure?

Sorry to pepper you with random questions. I've read a number of post on how to charge system but this will be my first full ac rebuild & thus I'm a little lost. Not to mention I truely don't understand the function of all the various main components (rec./drier, exp. valve, evap, freon, comp., etc) that make up an ac system.

I'm not GSXR ..But:

1. How can I tell if my evaporator is bad? I don't want to reassemble the dash if it's bad.
Visually is there signs of oil residue? That would be leakage.

2. How do I test for no freon leaks on my 134 ac system? Can I use my trusted Might Vac? I've got to replace the receiver / drier (INDY shop charged system a year ago I told me that's why it gets cool but not cold) because it's not blowing cold & thus replace freon but I wanted to test for leaks prior to removing rec./drier.

You can recover the freon, add dry nitrogen to 200# with a bit of R-22 and it will be easy to sniff test for leaks. Beyond that, you should charge the system.

3. I can spin the front wheel of the compressor so I'm assuming it's good. Can I add compressor oil without removing the compressor? How do you know if the compressor is engaging.

You can add oil with the compressor running via the low pressure line (adapter), or even put a squeeze type 1 oz charge (auto zone). If you've got the system open and replace the R/D replace all the o-ring seals and add oil to the dryer plus maybe 1 extra ounce. I don't have the system component capacity handy.

4. Should I go ahead & replace the expansion valve also? I think it's the original but not sure?
You should learn the functionn of all the components. This is not really difficult system. Pump, valve, evap, condensor and a R/D. If you take the system open, I'd put a new expansion valve in it - I got one at the dealership last week for my W124 and it was $44.

I've got a leak in mine- unfound, but a trusted pro checked the evaporator last charge. Now this past week, pressures didn't work out and it's most likely a failed Expansion valve. I'll recover the freon-then...
I'll do o-rings, flushing the system(coils), expansion valve, get the manifold rebuilt, and back flush it first. New oil, dryer and if needed compressor seals. Pull a hard vacuum for 2-4 hours and if it holds. Charge it back up with 1200g of R-12.
Hopefully that will put it in place. I'll look the condensor over really well for oil residue- but I'm guessing an o-ring on the compressor manifold hose.

Michael

Hi all!

Thanks for the great write up on testing the pods.

I have no or largely delayed air to the floot vents. Every other vent works normally as changes fairly quickly (within 30 seconds).

I pulled the glovebox and tested all of the pods. They all checked out ok, including #3 footwell flaps. I even tried it with the car on, and the flaps changed over right away on the MityVac.

Does this mean my pushbutton unit is bad? Or where can I go from here?

Thanks for any advice. 1992 300D 2.5 Turbo, almost 230k.

-m

PS: My pushbutton unit is a 124 830 3185 part number

The footwell flaps only open when the heat is on. I'm assuming you don't get any heat out the footwell flaps. In that case, since you've proved the vacuum portion is good...

1) Are you sure there is vacuum present at the top of the 7-port manifold, with the engine running? If not, find the broken or disconnected vacuum line in the engine compartment.

2) The 7-port manifold might be bad. This would be harder to test, you'd have to find the wire that corresponds to the footwell flap outlet, and check for voltage when the heater is on.

3) If the signal from the PB unit is correct, then it's probably a bad pushbutton unit. The part number you provided is correct for that year/model.

:scholar:

Hey gsxr,


1. I assume so as all of the other flaps work properly.

2. Ok, I have the CD for the car, I can try to track that down.

3. Anyone have a spare pushbutton unit in Minneapolis, St. Paul, I could borrow?! :)

Thanks for the troubleshooting. I'll dig futher.

-m

I wonder why the recirc flap has two big vacuum pods that move in unison. Doesn't seem like it would need two.

BTW, in the factory ACC manual there is a four-step process to check the different vacuum circuits without removing the glovebox.

If you find a problem you then remove the glovebox to test the individual pods.

Loud slap from center vent
 

This seems like too simple a question for this impressive review, but I can’t resist asking the question, since I am sure you will know what my problem is.

I get a very loud slapping sound from the center of the dash when I start my car with my climate control set in “auto” mode. It does not slap if I keep the control set to low fan. Is there something that would cause my vents to slap shut with such a loud noise?

I suspect it may be some kind of a vacuum thing, but it would be great to have a definitive answer and a possibly a little direction about a possible remedy.


Thank you for your help

SOunds like the vaccum check is in order.

My problem is simpler, uh, doh, my 95 W124 DONT HAVE A GLOVE BOX!

I beleive it was "commandeered" for the SRS airbag.
Yes?

It sounds like the main air flap is closing. But, I don't think it should make a noise like that. I wonder if one of the pods going bad could cause that? Hmmm. Wouldn't hurt to pull the passenger airbag and check the 7 lines, see if they hold vacuum when tested with a MityVac. Does it do the same thing if you are in "EC" mode or not?

Yes. To remove it:

1) Disconnect the negative battery cable
2) Pull up the front carpet under the passenger's feet
3) Remove the 1 screw holding the plastic or metal shield in place
4) Unplug the big red connector (this is for the airbag system)
5) Unscrew the one long bolt that holds the airbag in place (bottom/center)
6) Pull airbag forward, unplug connector
7) Installation is the reverse of removal.

:scholar:

Cool, THNX DAve!

Perhaps this is the same thing that I had. Mine would make a very fast slapping noise, more like a rattle, it was so fast.

It turned out to be the vacuum unit behind the glove box that has been mentioned in this thread so many times.

Mine would rattle based on the position of the temp wheel, coldest be the problem.

I have not tried that. I will set it to "EC" tonight and see if it slaps in the morning. Mine is just one big loud slap and it only happens once.

Thanks for getting back to me gxsr. As usual, you are wealth of information about these cars.

I think you must also be AMGDave from Benzworld, since I ended up at your site when I was looking at some things. I am still longing to get the big swaybars and I happened onto your post about your sportline bars being for sale. I'm still not ready to buy, however, since I have a number of "normal" maintenance issues to deal with. One of these days I am planning to jump in and upgrade to the sportline plus option.

Dave, thanks for all the help this has been a great post. Now, how much vac. should be supplied to the manifold? I get about 2in at idle and 3-4 at higher RPM's. I assume this is not enough. Where does the supply come from? I cannot find the vac line with the same color combination under the hood anywhere. Any pointers? I am fortunate in that only the number 3 line didn't hold vac.

You should see 20-25" of vacuum. The source is the vacuum pump on the front of the engine... a small hose comes up by the water neck, to a 4-way splitter. Two hoses go to the air filter area to feed the smog junk (you can disconnect and plug these to kill the EGR and ARV). The other two go towards the engine... one feeds the transmission shift circuit (feeds the vac control valve on the side of the injection pump), the other goes past the brake booster and into the passenger compartment to feed the climate control pods. If any of the 4 main lines has a massive leak, you'll get almost no vacuum to the other lines. Sounds like you have a leak somewhere, time to track it down and fix it. To test the pump, connect your gauge directly to the small output. The power brakes would be dead if you had no vacuum though. Here's a photo of the vacuum pump:

http://www.w124performance.com/image.../vac_pump1.jpg

If the only failed pod is the #3 circuit, you are VERY lucky. That is the footwell pod, which can be replaced without pulling the dash. You'll need to remove the pushbutton unit to access this.

http://www.w124performance.com/service/w124CD1/Program/Climate/83-620.pdf#page=1

:scholar:

Invaluable thread :)

Where is good place to get a CD of the shop manual? I tried the down load a couple of pages back but was ask for a password. I need to let a machanic friend see the dash removal vacuum pod replacement section if the leak check goes bad tomorrow.

Man the weather changed big time here and it is all I can do to walk from one end of the house to the other, or type here. I think I am signing off for now guys.

The ACC manual is a separate manual in the paper version.

I don't know if it's included on the CDs.

Well I should know in a couple hours if I need it or not. I haven't even checked the pods to see if they all work, I think it may have been subconscious fear of them not working. :o