126 climate control problem - PeachParts Mercedes-Benz Forum

lakeside · #1 08-15-2007, 04:09 PM

I'm about to order a new climate control unit but before I do, I'd appreciate your thoughts. (I did a search.) I have a 1988 420 SEL with about 130K miles. The air conditioning doesn't cool. My mechanic has checked all the refrigerant-circuit elements and the refrigerant pressure and all are working as they should. He believes the air mixing door inside is not opening properly for controlling the air temperature.

I trust this mechanic's diagnosis because he has repaired a number of problems with my SEL.

The air conditioning cools slightly, but not enough for our 100+ temperatures. I've read that the vacuum actuators may be bad, and I would order those but I don't see that part listed on this site. I need to get this fixed as soon as possible because this is our daily car, and my wife doesn't like to sweat.
Jerry

david s poole · #2 08-15-2007, 04:46 PM

easy fix temporarily,take out glove box and you will see fresh air door.make a short pce of two by four and cut a v in it so that you can wedge the fresh air door closed.the default is for it to be completely open,and you don't have enough capacity to take in 100+ air and cool it down.

lakeside · #3 08-15-2007, 05:00 PM

Thanks a million for the suggestion. I called my mechanic and that's what he's going to do.
Jerry

ntxsec · #4 08-16-2007, 01:52 AM

So David does the recirculate button completely close the door? My recirculate button seems to close the door but I still am unable to get cold air at 100+ degrees F. BTW I have an 89 SEC with the passenger side airbag so I don't know how to get to the airbox without messing with removing the airbag.

Dwain

david s poole · #5 08-16-2007, 01:09 PM

from what i recall the recirc button is for closing the fresh air door when outside odours are a problem.when temp wheel is lowered to the detent it should close the door all the way.the pass side airbag should be held in by one big bolt from the bottom but you can pry up the grill in front of the windshield on pass side[watch out for clips] and see the fresh air door.what are the pressures and temps when system running but not cooling enough?

ntxsec · #6 08-22-2007, 12:04 AM

I dont have guages for the system but will probably buy a set soon. Over the weekend I installed the 1.1 resistor on the aux fan temp switch as recommended by others on here and it has kept my engine temps below 100C and seemed to improve the performance of the A/C. The true test will be when we reach 100+F again.