W124: No air blowing thru central vents.

[juribe2]

Hi,
I think my car has some kind of problem with the A/C system but I'm not sure. The AC is blowing cool air but only thru the driver and passenger vents. I get no air at all blowing thru the central vents. What should I look for?

Thanks for your help guys.

[Larry Delor]

If you do a search, you will find that you most likely have a busted vacuum pod. fun fun

[psfred]

Make sure the center vent manual flap is open first! You will also not get cold air out until it switches to full AC mode. Quick check, turn the temp dial all the way down till it clicks, will blow out then unless you have a vac leak or a bad servo.

Servos can be tested, the switchover valve is beside the glove box, pull the liner and check each line for ability to hold vac. I'd also replace the right angle fitting with new MB ones, they get old and shrink and leak.

Peter

[brewtoo]

All you could want to know:

W124 climate control vacuum pod replacement

[juribe2]

Originally Posted by psfred

Make sure the center vent manual flap is open first! You will also not get cold air out until it switches to full AC mode. Quick check, turn the temp dial all the way down till it clicks, will blow out then unless you have a vac leak or a bad servo.

Servos can be tested, the switchover valve is beside the glove box, pull the liner and check each line for ability to hold vac. I'd also replace the right angle fitting with new MB ones, they get old and shrink and leak.

Peter

Thank you for your imputs. The central vent doesn't blow at all and I noticed that the recirculating function is not working either because I get external smells into the cabin.

I'm sorry but I'm totally new to A/C and vacum systems and don't know were to start looking. I don't feel like removing all the dash without knowing what to look for. Is there some kind of diagram or pictures to help me locate those componets (switchover valve, pods, servos, etc)?. BTW, my car doesn't have a glove box on the passager side. Only an airbag there. Or do you mean the box in the central console?

Thanks again guys.

[evansdave]

Easiest way to eval AC issues on the W124 (mine is 95 E300D) is to start w basics:
1. Does the blower fan work on basic ECON circulation? Good.
2. Does engine idle drop when the AC is turned on? Good, AC comp is OK;
3. Does cold air come out the side vents and defrost? Good, the AC circ system is working;
4. Does cold air come out of the *center* vent? (most common problem....)
4a: Check the 3-way vacuum check-valve just near the brake booster;
4b: Test all ports on check valve, plugging remaining;
4b: Test lines off of valve: green is center, red is lower interior air valves
4b1: Put a vacuum on each, and test the rubber fittings on and off
4b2: If the vacuum holds on the red/green lines, lines and all beyond is good;
4b3: Put rubber fittings on and re-test: if it leaks, its the rubber fitting. Replace.
4b4: if red/green will not hold vacuum, problem is under dash....

It's generally the rubber pre-formed piping connectors that fail; you can replace or just use length of standard vacuum hose. If the lines won't hold a vaccuum (red or green) then follow the instructions to gain access to interior valves: red is behind climate control dash module; green is behind air bag and semi-accessible from under dash.

[compress ignite]

Zomebody in an earlier reply HAS TRIED to steer you towards:

W124 Performance

It's Dave's ( Screen name GSXR )
COMPLETE Tutorial on all things W124

Literally, You Can spend Days educating yourself on it's pages !!!

The portion that deals with hvac is :

W124 climate control vacuum pod replacement

Why run yourself ragged?
Dave's already done all of the work . All you have to do is follow his instructions.