Fan will not run - 1999 Oldsmobile Cutlass

Cooling fan is controlled by a relay and a temp sensor. You need to check that each piece is working.
Run power to the fan. fan run? fan ok.
Bridge the relay. Fan run? run power to the relay coil. Fan run? relay good.
find temp sensor. replace.

Have you tried changing the fan relays? Sounds like they may be stuck on.

most time coolant temperature sensor faulty.but check cooling fan fuse and relay.then hot wire the cooling fan if fan runs.problem in the fan wiring or pcm.if every thing else okay.if cooling fan dont run when hot wired the cooling fan need replacing fan motor has internal open winding circuit.

The first thing is to test fan motor, unplug it and test it by powering it up to see if it runs, if fan runs then the next thing is to check the fan switch sensor, this is the sensor that controls the fan, jump connector to see if fan runs, if the fan runs then fan and relay are good and mostlikely its the switch sensor,

You have a radiator fan motor that is not running either due to a thermostatically controlled temp switch,(Located on the back of the radiator) a failed fan relay (in the engine compartment fuse /relay box) or a bad fan motor.
You can troubleshoot by checking for 12V DC to chassis ground at the fan motor temp switch. If you have power in you can jumper with a wire the switch wires and see if the fan runs. If it does not run then you need to check the fan relay and motor.

To test the fan you can run a wire from the battery to the fan and another wire to chassis ground to see if the fan runs. If after directly connecting 12V DC to the fan motor and it does not run the fan has failed.

As far as the you either replace it with another one or... have to figure out which 2 wires control the fan motor and jumper them out to see if the fan runs.

Kelly

check fuse and relay.if all is good.hot wire cooling fan using jumper wires to battery.if fan dont run replace the fan.if fan does run you have a open wire or bad connection at cooling fan electrical connector.

One fan should run when engine is running. Other fan should run when AC is on.

2006 mini cooper s power steering fan seezed. replaced with new fan won't run?

The tempature switch for the fan will be located on the radiator tank, most likly near the bottom or mid way up. It will have two wires in most cases.

With the key on but the car not running, connect these two wires together. If the fan runs, replace this radiator switch.

If the fan does not run, pull the connectors apart going to the fan itself. Jump power and ground to each of these two wires. If the fan does not run, the problem is the fan. If it does run, the problem is most likely the relay for this fan

Good Luck!

Have you confirmed the fan has a good ground, sounds like you have eliminated the issue of 12 volts, when you turn on the fan then the AC does the compressor run? if the compressor runs pull the plug to the fan motor and check to see if has 12 volts with a test light, wait for moment because the fan may not run until the AC system pressure reaches a certain pressure point, this means that even though the compressor is running the fan may not always run, There is a quick test for the fan circuit, disconnect the fan sensor at the thermostat housing, the fan should come on, this is failure mode, so if the switch goes open the fan will run to keep the engine from overheating , let me know after the tests are run.