Hi daveschmit. Welcome to the forum. This sounds typical of a failing motor. Actually, not the motor itself but the thermal cutout inside the motor. It's an overload protection device that causes way more trouble than it prevents. The contacts become pitted resulting in heat buildup and the device opening the circuit until it cools down and resets.
One local used car dealer solves the problem by disassembling the motors and bypassing the thermal device, but in my opinion, that leaves them open to a lawsuit if it can be proven they did that, and of course, it actually resulted in a problem. Some GM vehicles use way over-engineered window switches with relays built in. If one of those relays would stick and keep power applied, a window motor could overheat. That's why the thermal cutout is needed.
Use a cheap digital voltmeter to measure the voltage between the two wires right at the motor connector. If the voltage is still there when the motor stops working, you'll know the switch and wiring are ok. That just leaves the motor as suspect.
Saturday, August 21st, 2010 AT 3:13 PM