Heat all the time- replaced MonoValve - PeachParts Mercedes-Benz Forum

BTWTampa · #1 03-08-2007, 12:58 PM

Was receiving no heat, so checked the monovalve as noted in this forum. Found the rubber seal on the valve broken, so ordered and replaced the valve. Now I have heat all the time. A/C works great (yes, I'm in Florida where we need it in February) until the engine heats up, the heat overpowers the A/C. Removed the monovalve and reinstalled again, just in case there was some binding. No difference.

Any suggestions on how I can cut off the hot water from flowing into the heat exchanger?

Thanks
Brian

zcc · #2 03-08-2007, 01:35 PM

What is the car model, class and engine size???

david s poole · #3 03-08-2007, 05:10 PM

you must have broken one of the wires at the plug because the valve needs power to shut off.check the plug carefully.

brewtoo · #4 03-08-2007, 09:11 PM

Mr. Poole is correct. The default for the valve is OPEN and it must receive power to CLOSE.

BTWTampa · #5 03-10-2007, 07:54 AM

The car is a 1986 420 SEL.

I unplugged the connection and with the engin running, checked the voltage in the plug. Receiving full voltage if interior temp control is full cold or full hot. I didn't allow car to warm up fully, so maybe there is some control that gives full power until engine is operating temp.

My only guess is that there is a broken wire in the coil that goes around the magnetic monovalve plunger. Any thoughts on a way to check this?

Brian

brewtoo · #6 03-10-2007, 08:21 AM

Why don't you just check it with an ohm meter? Does your volt meter not have that function?

BTWTampa · #7 03-10-2007, 08:48 AM

Will do today and update you.
Brian

david s poole · #8 03-10-2007, 10:16 AM

did you use all the large washers when you put it back together and only change out the spring washer that was provided with the kit?and did you note the order of the washers and put back the same way?based on your description this can be the only other problem.

BTWTampa · #9 03-14-2007, 06:35 PM

Checked the washers, and based on the pictures in the forum, the washers are correct. I did not receive a new "wave" washer, but mine is in good shape, very little corrosion.

With power to the monovalve, washers correct, good continuity in the electric coil and not seeing any other problem, my guess is that the monovalve I purchased is bad. Is there a way to check it, outside of the car?

Brian

Paul · #10 03-15-2007, 12:28 AM

If you're getting hot air all the time your auxilary heat pump may be out. That could throw the cc into fault mode. you'll get heat from the defrost vents only. Try unplugging the pump.
Paul