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Just an FYI, the duo-valves failsafe open (no power to them at all). Reason being if it is really cold you'll need the heat. Now for the fun part John. When the car is first started (hoses are cold) set the dials full range cold. Then take an analog voltmeter (with an old type scale meter movement), set for the (if memory serves me) 15 volt scale, and check for pulses from the control head at each solenoid while dials are set for cold and fan is on (leave the A/C button OFF so the compressor doesn't run). When calling for cool those duo-valve coils pulse faster closing the flow in the heater coils (test each side without touching them together). If your only by yourself, set the voltmeter up first and then start the car with dials full cool (your only checking the duo-valve pulses). You should get the highest pulse (farthest swing of meter movement) with the 2 dials full cold. IF you get no pulses with dials at full cool while the fan is ON, your not getting power to them and the coolant is circulating through the heater coils. Good luck! .


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