87 420sel no heat

[kegger]

I have a 87 420sel with 165k, can not get heat to blow hot, fan seems to be working fine and antifreeze is ok, possible mono valve?

[rocky raccoon]

Monovalve diaphragm is a common failure on Benzs of that year range. Easy to check. Locate the monovalve, remove four screws and lift the solenoid out of the valve body. Inspect the diaphragm for a split. If bad, repair kits are available at a reasonable cost from many sources including Phil on ths site. Replacing the entire monovalve is a much more expensive proposition and is usually not required.

If the diaphragm is not the problem, make sure the solenoid is working (feel it or hear it). If not, it is electrical troubleshhoting time.

[kegger]

Yep, diaphram has tear, looks like a simple enough repair. How can I find Phil?

[TX76513]

Phil is HERE