The climate control on my 1995 E300D seems to work perfectly EXCEPT that the air flow at the vents seems weak. Heat is hot, AC is cold, variable speed blower is fine. I get SOME air flow, just not as much as I should, at least compared to other W124s that I'm used to.

My first thought was to replace cabin filters. Did that, but didn't help.

What do I check next?

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Remove the glove box liner to expose the switchover valve, a vertical piece with hoses connected to it. Remove the hoses one at a time and apply a vacuum and see if they will hold the vacuum. If only one will not hold vacuum, see if it is the defroster pod which is immediately to the left of the glovebox. If you are lucky enough for that one to be the problem(probably not with those symptoms) replace it alone since you can access it.

If any of the other pods are leaking it is a major job to pull the dash, so don't even dream of replacing one without replacing them all while you're there.

One other thing, before ripping off the dash, make sure you are getting a strong vacuum TO the switchover valve.

Hope this helps.

Sounds like your blower motor is installed backwards. I had the same symptoms with my 95 E300D, all CC functions worked and tested perfectly but airflow was weak. Opened up the blower motor housing and sure enough, someone prior to my ownership had installed the motor incorrectly. I reversed it and instantly had great airflow.

This was an original Bosch motor that is designed to install in the bracket only one way. They still screwed it up. The brush holder end of the motor should be toward the drivers side of the car. Rotation of the motor is toward the front of the car. In the attached image, the motor on the left is oriented correctly with image left being the front of the car. Take note of the way the fan blades "hook". The motor on the right has the fan wheels installed backwards.

Don't get sucked into the whole vacuum pod thing. If all functions work correctly, that's not your problem. If you haven't laid eyes on that motor, open it up and check. For me it was a cheap and easy fix. Good luck!

Attached Thumbnails

 

Can you tell by the noise whether the fan is spinning at full speed? You could have a fault with the regulator or the fan itself. Should be pretty obvious when the hi-speed fan button is selected.

Yes, fan is definitely spinning at correct speeds (based on comparison of sounds with my other W124s).

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

That's interesting....thanks!

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

OK, then it's time to run the vacuum checks suggested by Larry. Your problem might be bad vacuum actuators (AKA pods) failing to open the doors. If you have a mityvac with a vacuum gauge attached, also check to insure that you get vacuum from the source - the problem could be further upstream.

Do you know how to safely remove the passenger airbag?

If you get to the blower motor, get some spray on evaporator cleaner like - AC-Safe Air Conditioner Coil Foaming Cleaner-AC-920 at The Home Depot

Sixto
87 300D