Climate control mania - PeachParts Mercedes-Benz Forum

cbjukraine · #1 10-26-2006, 03:35 AM

hey everyone, I'm new to the forum. I've been doing a lot of work to my car, especially the climate control system. I'm proud to say that I almost have it working properly... almost. I have two questions for you climate control experts out there.

1. Why can't I get the footwell flaps to open?

2. When the temp dial is set to a cool setting, or a setting that is cooler than the ambient temperature, the center vents open and stay open, even when the "off" button is depressed. Is this how the system is supposed to function?

I've narrowed the problem in #1 to an electrical issue. I know it's not vacuum, because I've gone to great lengths to find and eliminate leaks in the system. I've replaced leaking actuator pods and all of 5 of the vacuum change-over valves. All the pods hold a vacuum and the change-over solenoids click and engage when 12V is applied directly to them. I've measured the voltage at the plug for the #2 changeover valve that controls the footwell flaps. I always get 0 volts when the pushbutton unit is set to a setting that requires the footwell flaps to be open, ie temp dial in the red and "economy". You may think immediately that it is my pushbutton unit that is faulty, but I just had it remanufactured by GDL. I'm lost...

Could it be the temperature regulator behind the glove box, otherwise known as the ACC amp?

thanks...

cbjukraine · #2 10-26-2006, 03:36 AM

forgot to mention my car... it's an 84 300D

my123ca · #3 10-26-2006, 09:51 AM

The center flap should be open at cool setting and off position.

When your checking for voltage at the plug, ty to use another ground source. You can find out if its the pushbutton switches thats defective or a bad ground.

riethoven · #4 10-26-2006, 10:00 AM

Maybe you got a defective unit from GDL. I am not sure how the pushbutton unit and temperature control unit interact. There is also the Klima realy behind the brake booster, but I think that is for sensing the speed of the compressor in relation to the speed of the engine and it turns off the the compressor when the tranny kicks down.

Brian Carlton · #5 10-26-2006, 10:03 AM

Quote:

Originally Posted by riethoven

Maybe you got a defective unit from GDL. I am not sure how the pushbutton unit and temperature control unit interact. There is also the Klima realy behind the brake booster, but I think that is for sensing the speed of the compressor in relation to the speed of the engine and it turns off the the compressor when the tranny kicks down.

Doug, all vehicles prior to '85 don't have the Klima..........

riethoven · #6 10-26-2006, 10:21 AM

Quote:

Originally Posted by Brian Carlton

Doug, all vehicles prior to '85 don't have the Klima..........

Thanks Brian. I can always count on you to have the real facts. So does that mean that pre 1985 W123 and W126 don't have speed sensors on the compressors?

Brian Carlton · #7 10-26-2006, 12:12 PM

Quote:

Originally Posted by riethoven

Thanks Brian. I can always count on you to have the real facts. So does that mean that pre 1985 W123 and W126 don't have speed sensors on the compressors?

The advent of the speed sensor came about with the serpentine belt. If the compressor locks up, a sensor is needed to disengage the clutch and save the belt. With V-belts, it's not an issue. If the compressor locks up, you burn up the a/c belt.

Your 1985 has a Klima relay, but, AFAIK, it has no speed sensor on the compressor, as it's not required.