1980 300SD

I started work on my ACC today. Testing with the mity vac, looking at connections, etc...

I figured I'd start with the center vent and defrost pods. Testing revealed the defrost pod was kaput, the center vent pod was OK. Some poking around confirmed my suspicions. They are almost impossible to service without pulling the dash

I had the instrument cluster, glove box and center ACC panel out and it was impossible. No way I'm going through all the work to pull the dash...

Anyway, I decided to try pulling the drivers side defrost duct. It's held onto the center stack with flimsy staples and to the underside of the dash with metal tabs bent over.

I'm happy to report that it worked:



Out:



It was fiddly, but not really that hard!

This is what the factory setup looks like:



I also pulled the nozzle which is held on by 2 little metal clips.

The white pod is one of those double acting deals which controls the defrost flaps and the pink one is the center vent control. If the double acting pod craps out the center vent won't work

That's THREE vacuum connections to run two functions, one of which is redundant because there is a manual center vent cutoff.

Since my pink pod was working I just swapped it to the defrost position and I'm going to remove the automatic center vent flap.



Here's the center vent nozzle and register assembly:



The automatic flap:



Any input? I still need to check out the leg flap pod but if it's dead I'll probably just work around it.

I'm going to be using the semiservo for blower speed switching:



It works well for changing blower speed via the thumbwheel and the push buttons give some more control.

This weekend I plan on mapping the vacuum part of the push button assembly to see if I can get the defrost pot working when the defrost or bi-level switches are pressed. When the leg flaps are open it just pumps air into the doors which is weird...

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Jon, does this provide any or better access to the evaporator face for cleaning? I can see the TXV valve, do the evap can't be that far away.

And how did you make that thin peek-a boo view of the center pod?

Hammerwerfer

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1985 300DT 241,000 miles
1979 300SD 202,000 miles

Seeing as how you have manual shut offs for the center vent why don't you just remove the damper actuator all together and come up with a way to "lock" it into full open position?

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Jim

Center vents are for gauges!

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

I just went through the climate control for my 79 300TD. Ib the service manual there are testing procedures for each major circuit and then shows where each elements of that circuit is found. Mine has a servo like yours but the routing is obviously different. So I DIY t the link that I provided in my servo vacuum thread I provided will show yours if you don't have a service manual but I'm sure one for yours is around. The checking procedures made it much easier to work my way through it.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

This is my 2nd ACC redux. I gave the 1st one (daily driver) the full meal deal with a new amp, aluminum servo, new pods, etc. It's a great system and works fine but I don't want to spend the $$ on this car.

I'm shooting for more of a simpler/budget overhaul with this one.

I must have been hazy in my description but I'm doing what you suggested Jim. The white double pod originally controlled the defrost flaps and the pink one ran the center vent flap. I've removed the whole center vent flap assembly, pod and all, and moved the pink pod to the defrost flap.

Now the defrost is closed by one single-action pod. It's normally open like the original so the defrost flap will be open until vacuum is applied to the pod.

No control over the center vent now other than the manual slider. It'll be tough reaching up there to close it but I guess I'll manage

The peek-a-boo view is through the center vent slot with the register assembly removed. You can finesse it out after removing the rubber boot behind it and pulling the 2 phillips screws along the sides. The 2 vents are easy to pop out using a screwdriver to withdraw the little "pins" on either side and sliding them out.

Pulling all this stuff does help with heater core access but not much with the evaporator. Fortunately on the 116 you can do a pretty good "blind" cleaning through the inlet behind the glove box.

I did a thread on it here:

Evaporator cleaning, scope vid.

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Seeing as how you are making the mods in the awsome way that you are I would set this up just the opposite. Vacuum opens up defrost. Call it the south Ga design.

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Jim

My center vent in my 116.120 has started to become lazy. I suspect a leak in the pot. You say you removed it through the register opening????

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

I don't know why people are so afraid to pull their dashboards. It's really not that hard, and you have sooooo much more access to everything back there. Granted I've never pulled a 116 dash, but I've pulled several 123 dashes. I can have them out in 15-20 minutes.

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Well, I mapped the vacuum portion of the pushbutton switch and here's what I found:



#2 is the vacuum source from the engine and the dots indicate which nipples provide vacuum in each setting.

This setup opens the defrost flap with either "bi level" or "defrost" and it's closed with the other buttons depressed. It also open with no vacuum. That's one reason I went with the normally open pot. If vacuum to the system craps out I'll still have some defrost

The SG design revision Jim proposes would leave me without defrost in case of catastrophic ACC vacuum loss If he built it it would probable be OK but with my work the possibility of failure is always going to be higher Plus it was easier this way

Bench tests look good like this:



Vacuum source to #2 and defrost pod to #3



It would be TOUGH to replace the pods through the center vent if it were even possible at all. It was pretty hard changing them with the defrost duct and center vent assy removed!

I'm pretty sure that dash removal on a 116 requires removal of the center console. I know that you have to pull the A-pillar trim which is a PITA by itself.

So far this ACC simplification is looking promising! I'm hoping to use either a vacuum or electric signal from the pushbutton assy to trigger the leg flaps and a heater valve and just use the servo for blower switching...

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

During the summer months I want it to fail closed where the air will continue to come out the center vents. With that said though once the center vents are forced to stay open then it is not going to make that much difference.

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Jim

Looks like my switch mapping was shoddy It seems as if nipples 1,2 and 3 are connected. The only switching takes place on 4,5,6 and 7.

I hooked the defrost pod into #6 and it works! The defrost flap stays closed unless defrost or bi-level are selected

Unfortunately the leg flap pod is dead and it's DEEP in the center stack.

This is a great thread by Chris over on the org that shows it:

ACC overhaul - Heater box / evaporator removal

I'm happy just to have selectable defrost and different blower speeds though.

A pic of the center nozzle with auto flap removed:




Looks like I can run it with just one pod and 4 vacuum lines:



The middle black line is vacuum source, the purple line runs the defrost pod, the other black line runs the blower and compressor vacuum switches here:



The blue line only has vacuum when the defrost or bi level switches are pressed so I was thinking about finding a normally closed water valve to run that one to. Bi level or defrost would then = heat maybe...

SuperServo entering static vehicle trials:

SANY0030.AVI - YouTube

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Modified no flap nozzle installed:



Vent back in:



Half of the defrost duct installed:



I think I'm going to go with an Astro Van valve with vacuum control while I refine the SuperServo.

The valve is in this thread:

It's heater season! ACC fun...

I managed to dump all the vacuum/electric stuff behind the ACC panel:

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

This is my first post and I must thank you guys for your generous gift of wisdom and humor.I check this forum a lot to maintain my 83 300SD. I don,t have the skills of an "ARMY",but with your help I have enjoyed 67,000 miles with this car in two and half years. My heat and air came out in my face and the defrost. I don,t recall why,but I took the panel off below the steering column. I didn't get around to putting it back before I drove it. The heat now comes out on my body, oh how great it is! I tried the air the other day, it was never that great despite a new compressor,vacuum,and recharge. With said panel removed I feel the air soooo much better. All I can say is this is working for my needs. Again thank you guys!

Woo Hoo! I picked up a normally open heater valve for about $10 (1979 Chevy V8 PU) and plumbed it into the line running the defrost line. Now both the defrost vents and the heater valve remain closed unless either the Bi Level or Defrost buttons are depressed.

I may map out the servo vacuum switch and see if maybe I can use it to open the heat valve when it's rotated to the hot side.

The valve and associated crap:

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD