PeachParts Mercedes-Benz Forum - View Single Post

thayer · #4 03-23-2010, 08:23 PM

Quote:

Originally Posted by znuh

Sorry for that - with all buttons the compressor is not turning on - I attribute this to the system simply being out of refrigerant. With the first two buttons, I get fan and heat (as I should). With the other two buttons, I get absolutely nothing - no sounds of relays activating, no ducts moving, no heater motor activation.

If I was on Defrost or up/down, the system works normal. Go to floor or EC, and it's like the system was in OFF.

Ok, Here is what I know, and what I would do if my car were doing this. (this is all from memory)

do these tests with the car on, pushbutton on full, that is two white arrows pointing both up and down with the temp dial on full cold, turn until you feel the click.

1st. Compressor test. Jump the two wires going to the receiver dryer(while the car is on) and see if the clutch for the compressor engages. (that is the disc that doesn't spin while the accessories belt is.) If the compressor clicks on, then you are low on refrigerant.

If the clutch doesn't engage then test the evaporator temp sensor. This is the little box up and to the right of the accelerator pedal behind the carpet wall. It will have a sensor wire going into the evaporator. jump those wires and see if the compressor engages. If that is the compressor culprit, then you can do one of two things. Take a screwdriver and turn the tiny screw clockwise until it engages without being jumped, or purchase a new temp sensor without messing with the screw. The replacement temp sensor I bought did not have a screw or it had a tamper resistant cover over the screw. that parts job is to keep the evaporator from freezing which is pretty much death to the cold side of the climate control. the repair will overly total the car.

Now, if those don't activate the compressor clutch then I will defer to the more experienced members of the forum to deal with the compressor.

Blower issues.
If your blower is feeling it's age, it will require more current to spin. the non functioning buttons you are talking about take less current then the working ones. That leads me to believe that you may need to pull your blower motor and replace the brushes.

Test to see if the vacuum actuated flaps are flapping even though the blower is no engaging.

Flap test
With the car on, turn the climate control off. then press the econ button and listen for the vacuum flaps to move. cycle through the buttons specifically listening for the flaps to move. go from defrost to floor, full to EC ect.

If your flaps are moving and the blower is only coming on when set to high current options, I would look at replacing the brushes or the blower.

(I went in to disassemble my blower and found that it was replaced in 2003. I decided it wasn't the blower and moved on.

So, if it is the temp sensor for the compressor and the blower for the push button, then you aren't far from a fully functioning climate control system.

Good luck.

Kent