Fan not turning on/ changed thermo already?

my fan works with ac and when i unplug connector but will not come on by itself. temp will rise but not overheat. I just changed thermostat with no luck. Any ideas? 2001 Lumina.

If your still working the problem. When you start your car and the engine is still cold and you turn the A/C on, does the fans come on within one minute or does the engine have to be running for awhile?

my fan works with ac and when i unplug connector but will not come on by itself. temp will rise but not overheat. I just changed thermostat with no luck. Any ideas? 2001 Lumina.

the fan works so that is not the problem. the ac on the fan comes on this is normal.

with the ac off the fan comes on due to the temp reported to the PCM/computer. you must chenge the temperature sensors that reports this to the PCM.

these can cause the fan to come on when first starting in very cold weather[run all the time] or will not come on as the engine temp rises too far. the guage sender can also be defective.

There are two fans and they always run together. There are three relays. Without A/C, the fans run in series at approx 600 rpm. When the temp indicator reaches half way on the gage, the PCM (computer) will command the #1 fan relay to close, power runs thru #1 fan relay, #1 fan, de- energized #2 fan relay, #2 fan and then to ground. Need a multi meter and a wiring diagram. Check owners manual for fuses.