My recirc A/C function is not working and read in other posts that the actuator that controls the flap is behind the glove box. So I pulled the glove box and immediately you see an actuator (#1 in pic) that controls the defrost. If you look closely behind it, there's another pink actuator that I'm assuming is it, if at all. (#2)

Anyone know if I'm getting warm here? In the pic you'll also see a stack of vacuum lines. (they're numbered top to bottom) Do one of these lead to the fresh air flap, and if so which one?

I would appreciate a vacuum line diagram is someone has one handy for a '91 300E.



Thanks in advance!

~Paul

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'91 300E, 215K miles

I hate to be the bearer of bad news, Paul, but you are about 8 hours away from replacing your recirc vacuum actuators, if you can match MB flat rate times.

The actuators behind the glove box apply to the W126s, and are simple to replace. The actuators on a W124 are right in the center of your dashboard and are impossible to replace without removing the dashboard. Looking at your center vents, picture the actuators very near the windshield and about as far apart from each other as the width of your vents.

When you (or someone else) replaces them, don't stop there -- do all of the actuators. And, though one can purchase the vacuum diaphrams alone to repair them, I wouldn't think of doing that on a W124.

The first thing that I would do if I were you is to ascertain that your evaporator is not leaking. If it is, may as well do it, too, while you're in there -- it's a known problem on these cars and it is about 18 hours labor. Of course, this would subsume the 8 hours for the actuators if an evaporator replacement is needed.

Now, let me tell you about a temporary -- and only temporary -- fix until you replace the actuators. Go to Home Depot or Lowe's and buy some aluminum duct tape (not the cloth type, but the aluminum type) and open your hood. See the air intake for the HVAC? Take about 4 or 5 strips of the tape and completely seal the intake and you now have temporary recirculated air. Repair your car as soon as possible and, while using the tape, make sure that you take in some fresh air periodically in the car by rolling down a window briefly.

Richard Easley
Waco, Texas

Thanks Richard for the tip!

If you look at the placement of that 2nd actuator in the picture, it is positioned as close to the firewall as you can get and is directly behind the center vent as you described. Maybe I can replace that actuator and get 50% smog and 50% recirculated smog?

Just for curiosity's sake, could the recirculation switch itself be bad even though the little red light comes on? Also, does one hear the flap in the dash opening and closing from the pressure? Because I hear nothing when I hit the switch and no outside fumes seem to be held out of the cabin at all (80/20?), so I'm just assuming it is not working. How can one definitively test it?

Anyhow I'll use your temporary fix until I get a weekend to yank the dash.

Thanks again!

~Paul

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'91 300E, 215K miles

Paul:

I recently replaced the easy one behind the glove box, which is the defrost flap. It failed at around 125K. At first you will hear a liquid, squishy sort of noise, which is the rubber diaphragm. Then, for several days I was hearing a soft knocking from inside the console, which I suspect was the partially torn diaphragm flapping around from the vacuum. Eventually there was no sound at all. I'm not looking forward to doing the 3 under the dash, but I'm guessing I'll beat the 8 hours when I do.

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Jim Wiggin
Columbus, OH
1989 300E

I've posted this before, but here's what you'll be looking at. I would'nt get in a big hurry during disassembly! There are two elements at the top center of the black box and one inside it. Heck of a job but it makes all the difference in the operation.

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Is the situation the same on a 1991 190e? I understand there are five vacuum modules and if I change one, I should change them all. Can I do this without removing the dash? Also my blower has stopped spinning even though I get cold air out of the vents as I drive down the highway. I'm assuming I'll have to replace the blower and hope I can change that without removing the dash. Lastly, I get a fog blowing from the vents into the cockpit. Is there an easy way I can tell if the evaporator is leaking or if it is just condensation? I've never had that on any other car I've had with A/C before.

Thanks

The blower motor on the W201 is on the engine side of the firewall, in a box under the wiper motor/arm. Like the W124, replacement of the actuators, and more importantly the heater valve (weak point), is behind the dash.

My recirc A/c button goes off with a knocking sound inside the dashboard and the blower also slows down very much almost like it is off and then slowly picks up speed.this cycle continues. The outside temp is very hot like 46C and when the blower slows down and the recirc button goes off it is quite warm inside.
Is this difficult to fix.

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300CE 1989 Euro Model.
ML350 2011.