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My '90 764 GLT has a sunroof control issue. I was hearing the motor click only when pressing the top of the dash's toggle switch (to close sunroof). Of course, sunroof was not moving in either direction. It is stuck in almost closed position with a slight gap that still allows rainwater to pass through.
Following FAQ, I did some checks. At the electrical two-wire connector, I measure 13.5 voltage supply to motor through the Blue wire. At the same connector, I measure 9.5 V supply to the motor through the Red wire. At each location, I depressed the toggle switch. Motor shaft movement occurs from Blue wire's 13.5 V. No shaft movement from the Red wire's 9.5 V. When I swapped the wire voltage supply, I got the motor to reverse itself. Thus, I have concluded that the motor is not faulty. Oh, ground was cleaned as were fuse spade terminals to be certain of good tests.
Next, I pulled the dash sunroof switch and examined it. Four wires feed the switch. Gray-Red and Red wires on the driver's side. Blue and Black wires on the passenger side. One switch spade terminal appeared darkened, the terminal connecting to the Gray-Red wire.
With engine running, only the Gray-Red wire measured significant voltage, 13.38 V while all others were in single digit mV range. Measured resistance between switch's terminals on driver side and passenger side as I toggled switch in both directions. Infinite resistance on both sides toggling up. Toggling down was different. Driver side: 3.6 m-ohms; Passenger side: 1.4 ohms to 000.0 ohms.
1. I don't have an electrical diagram for the sunroof circuit so I don't understand the Gray-Red and Black wires descriptions leading up to the switch or how the switch's internals work. Seems similar to a power window switch is my guess.
2. Is there a relay for this circuit?
3. My electrical training to interpret these measurements in total is minimal but my hunch is that the switch is faulty.
4. Don't understand how the Red wire is presenting 9.5 V at the motor.
Thanks in advance for the help.
For the fun of Volvos,
Mike
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'92 245DL, '90 760 GLT
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