We have been going through the forum searching for ideas and found a few. Thank you!
96 Bonneville cooling fans are not turning on. When the temp sensor is disconnected, they both go on. Temp gauge on dash works (except when sensor disconnected). Coolant is full and has been burped at the thermostat housing provision.
From what we've read here it seems that if they go on that the relays and ECM should be working properly?? Fans will NOT go on with A/c turned on but the compressor is NG so no Freon in system. Could the temp sensor be the culprit even though it reads on the dash?

Thank you

Hi Paula, you didn't mention what temp you were getting up to without the fans coming on, I think the more knowledgeable members could tell you to the nth degree when they're supposed to come on but I think it'* in the 210-220 F range w/o a/c on. speaking of the a/c, if you're low on freon and probably a/c oil too, I would unplug it at the compressor clutch until you can have it charged. It may be that the relay to the cooling fans is bad, happened many years ago to my daughters first car, a pos 84 Cimarron, in that case tho the a/c worked fine, had to run the a/c to cool it down. I didn't want to spend a lot of $ on that car for her so I simply by-passed the relay so the fan ran all the time.

Fans will turn on at eng temp of 212F low speed and 226F high speed.

You are correct, the fans automatically turn on when you disconnect the temp sensor. This is called 'fail safe mode'. Its designed to do that.

The system will only turn the fans on if the above temps are met, OR, if your A/C is on, it see'* a certain pressure at your HIGH side pressure sensor. Because you have no freon/pressure in your a/c system, its not going to turn on and build pressure like its suppose to. No A/C, no fans.

So far, your system looks like its operating normally.

Thank you for the quick replies. What is bothering me is that even when the temp gauge goes into the red zone the fans do not come on. I'm not sure what the actual temp is but to me red means HOT. I don't have any method of checking the real temp though.

I wouldn't drive it if its getting that hot. If it really is.

Only way to test it is to have a shop look at the live data from the computer in the car. He can compare what the in-car-computer is seeing for an engine temp and compare it to what'* showing on the instrument cluster.

If you were closer, I'd come to you, but from the looks of it, your in the NYC area.