2000 C230 Dual Zone Thumbwheels

[kwmouser]

Hi all,
I have no control of the temperature on the passenger side; stays hot. Both sides stay hot with the duo valve electrical connector disconnected. Using a DC volt meter the center pin is common high and reads 12.56 to 13.79 VDC to each outside pin. There is no variance in voltage when either thumbwheel is rotated which is puzzling to me. I tend to think I should see some kind of potential variation in resistance on the return pins; at least on the side that does appear to be functioning correctly. I am going to cross jumper the valves and also run some resistance tests on the returns; other than that I am stumped. I would sure appreciate any help you have to offer. Thanks.

Ps. I had washed the engine compartment just prior to this anomaly; however all connections appear clean and free of oxidation.

 

[Blobcat]

Hi & Welcome,

I've moved this to the appropriate area of the forum

 

[television]

Welcome to the forum,,is the car a 202 or 203 please

 

[kwmouser]

Hi guys, thanks for the help, what a fantastic website!!! The car is a W202. Thanks again.

 

[Dec]

With the duo valve re-connected up try tapping the valves with the handle of a screwdriver, this might free it/them if the are sticking, remember it will take a few minutes for the air to cool at the vents in the cabin after you turn the thumb wheel to the cold setting
See also… http://forums.mercedesclub.org.uk/showthread.php?t=25909

Dec

 

[television]

The duo valves are controlled by a pulsed output form the control unit, so not easy to measure with any real meaning.

You mentioned that this happened after washing the engine compartment, the fuse /control box with 2 lids can leak water and under there you have a SAM unit where water can get underneath and give silly faults, though modified lids were brought out to stop this I do not know when or if the lids were ever changed during production

 

[kwmouser]

Just a quick status update; continuity test on the duo-valve shows that the coil of the passenger side solenoid is open. Next step will be valve disassembly to locate open and see if it is repairable or a replacement will be required. Will report on those findings when completed. Thanks to all, you have been of great help. Good bye for now.

 

[kwmouser]

Conclusion; open coil was on the inner winding lead broken inside the spool. Unable to repair. If break had been on the outer lead I could have taken out one wind and resoldered lead. I located a new Heater Valve at Autohaus Arizona for $138.95 USD and free shipping. Dealer quote was $220.00 prepaid order (not in stock). Used ones on eBay were listed at around $90.00 plus shipping. Thanks for all your help, it has been greater working with you. Cya.