96 Lumina cooling fans don't engage

[lesabrefan]

Guys, I've noticed a bubbling sound from the expansion tank and since have recognized that the fans are not engaging. Drove 20 miles and stopped three times to check, not engaging. I checked the relays under the hood on the passenger's side, they're good. What's my next step? How do I check the motors on the fans, I guess since both are not working, it can't be that both motoros failed simultaniously.

Thanks a bunch.

[jdl]

Does the fan run if you turn on the ac? If you unplug the coolant temp sensor, does it run? You may have to check wiring circuits at the relay, you may be missing voltage or ground for some reason.

[lesabrefan]

When I turn on the engine and AC is on, the fan on the left (if I'm standing in front and facing the engine) engages. When I turn the AC off, the fan keeps spinning. If I turn the engine on with AC off, the fan does not engage.

[lesabrefan]

How do i unplug ECT sensor, I found this explanation: http://www.ehow.com/how_4856815_trou...oling-fan.html , but it's unclear. I see a yellow and black wire coming out of the left fan (if I'm standing in front and facing the engine), but I can't see where it goes.
Thanks

[jdl]

The coolant temp sensor should be on or near the thermostat housing. The wiring colors are yellow and black.

[lesabrefan]

Can't see yellow/black wiring of any sort by the housing. There are two pieces near the entry point of the upper coolant tube, one that looks like a car cigarette lighter and the other thinner piece. Is one of them the ECT sensor. Both pieces are at 90` angle to the wires.