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Old 12-16-2014, 10:19 AM
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funola funola is offline
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Join Date: May 2005
Location: NYC
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Monovalve and ACC info/ troubleshooting thread

To start, I shot a video of a light bulb connected across the Monovalve to show its duty cycle under 3 different temp dial settings. This is my 85 300D where the climate control system is fully functional per descriptions in the owners manual. This is an easy temporary test to set up, however there are risks that is preventable.

Video was taken after the coolant gauge went to normal operating temp. Note the change in duty cycle of the bulb (on time vs off time).

Bulb on = no coolant flow

Bulb off = coolant flow

With temp dial turned to cooler setting (more blue showing vs red), you can see the bulb on time increasing and the off time decreasing. If you rig this test up and it does not behave similarly, it may point to problems in the climate control unit, the push button unit, the temp sensor etc.

Click to play video



For the bulb, I used fine stranded wire and wrapped/ twisted it around the monovalve terminals then taped the connections to keep them from shorting to each other, then put connector back on. Warning: Make this temporary connection WITH KEY OFF or you will blow a trace in the push button unit.




I will post more tests when I do them. If you have anything to contribute, please post them.
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83 300 D turbo 297K runs great. SOLD!
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