Quote:
Originally Posted by sides
Hi all,
Cruising down the highway two nights ago, suddenly the heat stopped working in my 300d. It just started blowing cold air. Interestingly, before it stopped, when the heat did work, it only blew out of one of the air vents. When it stopped and only blew cold air, it blew it hard out of all the air vents.
I've been reading here about the monovalve. Where is it and is that the problem? Any other ideas are greatly appreciated. It's getting cold.
Many thanks,
BS
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What year 300D is it?
From what you describe occurring with the air vents, it sounds more like you have a problem with the acutuators for the vent flappers (ie, vacuum problem), and/or a problem with the CCU itself.
A problem with the CCU itself would explain both symptoms - if the CCU went funky and decided to shift from heat to vent mode, that would explain the change in air flow from the vents, and commanding the monovalve shut would explain the sudden lack of heat.
The monovalve by itself going south wouldn't explain the change in air flow out of the vents.
A loss of vacuum to one or more of the vent flap actuators, depending on which ones, could explain both symptoms as well, but after experience with my two 87 300D's, I'm sort of doubtful of that.
I'd first do a vacuum test on the vent flap actuators, to eliminate that possibility. If they check out, check the monovalve and aux water pump to ensure they work and eliminate that possibility. If they're OK as well, I'd say you're left with a flaky CCU (for whatever reason) to blame.