87 560SL No heat
 

I took the suggestion of checking the monovalve. It looked like the rubber was in good shape, and I checked that it was getting power (13 Volts +-) . It is. Since it is not expensive to use a repair kit, I ordered one.
But I'm still not sure that this is the problem. Can anyone suggest any other possibility that I should be checking.

Steve Metz

the amps like to go bad.. Do you at least have heat on full defrost?

Jonathan

IF you un-plug the heater valve(electrical connector) you should get FULL heat. IF not then either the heater valve or heater core is plugged up!

One other possibility for no water flow thru the heater core... Is the aux. water pump functioning? You can easily check by it. It is located in the same vicinity as the heater valve. While there, check to see it is getting supply voltage to rule out power problems, etc...

Good Luck!