Center vents not blowing hard in 300E
 

Hello Board,

For the last week air has barely been blowing out of my center vents. When I turn my A/C on high, the air blows really really hard out of the driver and passenger vents, but the air comming out the center vents is really low, almost no air. I changed my blower motor fuse, but that did nothing.

Does anyone know what the culprit could be??

It means that the center vent vacuum diaphragm is on its way out. Major PITA to replace - requires removal of the dashboard! Does air come out of the defroster vents when th AC is on?

centre vent no air
 

My 1994 C180 has the same problem and was going like this for a couple of weeks. Then I decided to visit my indie and the night before that it started working like it read my mind. Its now still working, but I am not sure if it should blow continuously all the time like my Camry and Corolla. Is this a Benz feature that it keeps cycling the centre vents off and on every few minutes or according to engine speed or car speed? The side vents seem to be blowing all the time though. Is something wrong or going wrong? About 6 months ago I had the whole dash taken down by the same indie and he changed 2 vacuum diaphram actuators which were punctured or leaking. Now he says that "maybe" the controller of these sets is going out. Anyone with similar ideas or have better ideas? Is there such a thing in my car? Sometimes I don't know whom to believe in.

Before you try to remove entire dashboard, etc., see if by removing inner loiner of glove box and the lower passenger trim panel, you can get to the diaphram and lever/actuator. As a quick fix, you might be able to secure it in an open position by wedging some rubber in there. Worked for me, but this was on a W126 body car.

Does anyone know if this applies to the w124??


removing inner loiner of glove box and the lower passenger trim panel, you can get to the diaphram and lever/actuator. As a quick fix, you might be able to secure it in an open position by wedging some rubber in there. Worked for me, but this was on a W126 body car.

Check the vacuum line (green) in the engine compartment near the brake booster. Most likely there is a leak, usually rock hard rubber connectors that look like vac hose, and can be replaced with generic vac line from the auto parts store.

If the vents close on acceleration, it's almost definitely a leak unless you also have a bad running problem resulting in very low vac, and even then there is usually enough in the reservior to "coast" the AC over low vac condition.

Check all the rest of the vac lines at the same time, they are all probably in bad shape. Check the idle control valve hoses especially in the M103 and M102 engines, they will be rock hard and probably leaking -- causes throttle lag and rough idle.

Peter

Unfortunately on the W124, replacement of the center vent vacuum diaphragm requires removal of the dashboard. What you can do to test it, is pull the glovebox liner and look at the manifold which has a bunch of lines coming off it - hook a MityVac up to the one that controls the center vents (I forgot which one) and see if it holds vacuum. Actually, check to see if they ALL hold vacuum - which they should.

If you're pulling the dashboard, you might as well replace all the vacuum pods...

No, to get at the vacuum tree in a W124 (with the glove box, not the pass. airbag) you have to:

1. Remove the lamp assembly (just pull down from the from, held in place with two spring clips). You don't need to unplug the electrical connector, it can just hang.

2. Using a thin, flat screwdriver, pop off the plastic inserts around the outer edge of the glove box lining. They're two piece, inner and outer, compression fit, pry out the inner and both will come out.

3. Unscrew the two screws holding the glovebox latch plate, remove the plate. (Pay attention to how this goes together, there's the latch plate, the screws, and then another plate -removable and easily misplaced!- that goes into the dash frame that the screws anchor into).

4. Remove the glovebox liner. You'll have to pull down on the upper part of the liner near the latch plate, it has a lip that will catch on the metal dash frame if you don't.

5. The vacuum junction box is on the lower left.