PeachParts Mercedes-Benz Forum - View Single Post

pawoSD · #8 11-13-2013, 08:56 AM

Quote:

Originally Posted by Junkman

I was told by my local indy who has worked on these things since they were new that the entire monovalve needs to be changed if disconnected and no heat at speed. The unplugged monovalve defaults to full heat period. He said it was a yes/no question and not to over think it.

He also showed me a 12v test light that he used to use for testing the temp control. It was basically 2 wires and a bulb cut from a harness. He said that the light would come on if the temp wheel was turned to high heat. If not, something is wrong with the dial.

He also said to change the auxillary pump if the push button needed changing. The pump can take out the push button CCU.

His recommendation to replace the whole thing is not correct. The housing itself it just a static piece of plastic. There is then the magnet piece at the top, which can fail, and the valve piece with the spring and diaphragm. Those two components are the only "wear" items. No need to ever replace the whole unit unless its cracked or leaking etc...

Its possible you have a flap issue with the heat-door in the dash that is causing it to improperly close at higher speeds, leading to no heat. Especially if its doing it with the monovalve unplugged.

I would do the test with a bulb to see if the klima unit is sending power to the monovalve at the correct temp wheel settings.