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Where on my car can I find the mono valve. I am having the same problem as Ken with the heater blows full hot 90% of the time. It does not seem to matter what the CC dial is set on. Sounds like I need to check this item out. I have done the form tube replacement.

I am also open to any other suggestions?

Ron

I assume we a talking about an 83 300D, the monovalve is on the firewall right next to the battery, it has two heater hoses and a wiring connection.

Hey Craig,

Thanks for the speedy reply. I will be checking my mono valve this weekend. Yes my car is a 1983 300 D Turbo. I am having the problem with the heat blowing full heat most of the time.Do you have any other suggestions. Anything I should know about checking this thing?

Ron

I would start by checking fuse #14, if it is blown the monovalve will be fuly open. On the valve itself, you can open the top and make sure the diaphragm is not damaged. The internals look like this, and you can buy a repair kit if this is the problem:

Mono valve links thread


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RonB,

Please update your signature in the "User CP" with your car's info. It makes answering the questions a lot easier.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Done