temp light comes on sometimes

I own a 90 Lumina with a 3.1. My problem is with the temp light. It will come on pretty much as soon as it's started. It goes out when I'm accelerating or when the engine seems to be working more. Other than that it stays on most of the time. I thought it was the ect sensor so I changed that but it made no difference. I'm wondering if it's in the wiring or elsewhere. I really hate electrical stuff. Would I have to bleed the coolant system after changing the sensor or would it not be a factor.

Any tips would be greatly appreciated.

Thanks

Do you have the guage or just the dummy light? I think these have a seperate temp sensor mounted on the head for the guage/light, and the ECT just feeds to the PCM. If that doesn't work, yes, it could be in the wiring. Does the engine actually reach critical temp? I would assume not since the light won't come on until 260+ degrees, IIRC, and at that point you start to warp and crack heads...

Fans turn on all right? Known good thermostat? Just trying to rattle out ideas that I've got...

Just the idiot light. I never thought to check for the fan or anything like that. I'll try it.