[mtnaggie]

Greetings All ~

This past summer the mono valve in my '84 CD stopped functioning. No problem I thought. I read up on the DIY side and slipped in a rebuild kit, though the rubber on the existing part appeared intact. When that didn't solve it immediately, I then just by-passed it to make it through a busy summer.

Now I pulled out my spare parts bin, and grabbed an extra valve, but the same result. Tried changing out the CCUs with a spare and still no mono valve control. Finally checked voltages. One of the two leads has 12 volts at all times the key is on regardless of the CCU position. If I turn the CCU to activate the mono valve, the other wire has around 10.5 volts; this should go to ground, right? Read all the posts and treads I can find and still can't find a solution.

I would appreciate any help anyone can give. NE Texas will require A/C in the dead of winter to other areas, and I can't just ignore this problem.

Thanks!

 

[Commuter]

When you say it stopped functioning, does it not allow coolant flow or does it not stop flow?

The valve normally open. It allows flow when the mono valves coil is not energized. When the circuit is grounded by the controller the coil is energized and the valve closes, stopping flow of coolant to the heater core.

The voltages reported sound reasonable for when the circuit is grounded and the valve is closed. The 12 volts is the system voltage and the 10.5 volts is the voltage drop across the coil. If it were not grounded you would see the same voltage on both sides of the coil because there would be no current to cause a voltage drop.

If you disconnect the connector on the mono valve you should get heat when the engine is running and hot. If the coil is energized when the should be giving heat, the relay is stuck closed for some reason.

The information in the following link may help.
http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Climate/83-600a.pdf