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'83 300D heat poor without monovalve??

847 views 1 reply 2 participants last post by  Cycobilly 
#1 ·
I have an 83 and 85 with the same type climate control... The 85 wagon has fire-of-Hades heat, ever since replacing the monovalve two years ago. Torn diaphragm. The '83 was not so blessed in the heat dept, this is our first winter with it. Yanked the monovalve and found similarly torn diaphragm, replaced with new rebuild kit. Heat still not great. Stays hot for a few minutes then fades to lukewarm.

So here is the weird part. Behaves the same after unplugging the monovalve, which opens it and produces max flow. Any reason ASIDE from clogged heater core this should even be possible?? I would think you're going to get hot air with an intact but disconnected monovalve but that is not what happens.
 
#2 ·
A stuck or missing thermostat could prevent your engine from warming up enough is another possibility.
 
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