W124 Heating and Cooling Air Vent Question - PeachParts Mercedes-Benz Forum

Oldwolf · #1 10-06-2010, 02:06 PM

Heating or cooling I don’t get much air out of the upper passenger vent. Now, looking at air flow diagrams I should always have air flow out of them. The center vent and lower vents are modulated during varying temperature conditions. It looks like a straight path from the main air plenum that houses the coils to the left and right vents. So I don’t see why the vents would be closed. Maybe the ducting hose slipped off since there seems to be no damper there to malfunction. Anyone else seen this in their W124?

ps2cho · #2 10-06-2010, 06:43 PM

Your main center flap (40) vacuum pod is probably toast and that's why it stays shut. You can replace it without removing the entire box. Just pull the dash off and you should be able to replace it.

Confirm via the vacuum switch behind the glovebox though. Pull off each vacuum cable individually and use a mityvac or similiar to check vacuum.

Oldwolf · #3 10-06-2010, 06:59 PM

The air shuts off and on fine on the central vent, which is pod 40 I think. It is just the upper passenger side vent that doesn't flow so well. I don't see a vacuum pods for the side vents?

ps2cho · #4 10-06-2010, 07:18 PM

Maybe the air diverter (41) has failed then?

Either way you can't tell until you check if any of the pods are not holding vacuum.

Cal Learner · #5 10-07-2010, 05:54 AM

Side vents have no pods. Open all the time.

Oldwolf · #6 10-07-2010, 08:58 AM

Quote:

Originally Posted by Cal Learner

Side vents have no pods. Open all the time.

That's why I'm hoping the vent is disconnected in some fashion. I've never yet had the panel above the passengers feet to look.

macdrone · #7 10-07-2010, 12:49 PM

Pull out the glove box/passenger airbag and see if its disconnected. Also dont laugh too hard but check and make sure thumb wheel works and is connected and fully open.

Oldwolf · #8 10-07-2010, 01:39 PM

I didn't know the passenger air bag was removable by owner. I guess I'll need to figure out how to do that. The damper seems to be working OK when I look in to the vent.

macdrone · #9 10-08-2010, 10:16 AM

The air bag has 1 bolt from underneath, unhook battery and pull it out.

Oldwolf · #10 10-08-2010, 10:28 AM

Quote:

Originally Posted by macdrone

The air bag has 1 bolt from underneath, unhook battery and pull it out.

That pretty easy. It won't pop my head off when removing will it?

macdrone · #11 10-08-2010, 04:35 PM

dont disconnect the wires just to make sure but there is always a danger. Just tug it straight out and look at the tube, reconnect if it is off and push the bag back in. Its quick and easy to check.

Oldwolf · #12 10-11-2010, 07:25 PM

Turns out I can see the black plastic flex duct that goes from the evaporator box to the passenger vent if I crick my head down in the foot well and look up. I had barely enough hand clearance to feel that the flex duct was disconnected from the rear of the vent. Plus, I could shine a light up and see it through the vent.

In what has to be for me the easiest fix I managed to stick my hand up and grab hold of the flex duct and snap it into place on the vent.

I cranked up the A/C and now air is flowing form all vents. Yeah!