My radiator cooling fan is not working why?

This is most likely one of two issues based on everything you replaced. Either you have an issue with the PCM not commanding them on the proper speed, or you have resistance in the wiring.

Try jumping 12 volts directly to each fan motor to ensure they are capable of spinning at high speed.

If they can, then you are not getting 12 volts to them when you should. Again, either the control module is not sending 12 volts or the wiring has high resistance not allowing the motors to get 12 volts.

You can confirm this by measuring the voltage you have at each fan when the A/C is on and the coolant temp get higher. Both fans should be on high at this point.

At that point, you want to measure resistance from the relay to the motor. Then to the PCM.

https://www.2carpros.com/articles/how-to-check-wiring

Let me know what questions you have. Thanks

GM fans in that vehicle turn on at 223 degrees and turn on for the AC if the air temperature is over 122 degrees. The only item you may want to check is the actual AC pressures and the pressure switch. It should activate at pressures over 190 psi. And turn on the fan. If you have access to a shop or an OEM level scan tool you can test the fans operation very easily and without touching anything under the hood until you have determined if there is a problem.

221 degrees is not hot enough for most GM vehicles. They need to get much hotter than other brands before the radiator fan will turn on. I always remember 226 degrees, but some experts say it can be even higher.

On most cars you can force the engine computer to turn on the radiator fan by unplugging the two-wire coolant temperature sensor. Turning the fan on is the default in case the engine is getting too hot. The computer will not know it, so it runs the fan to be safe. Doing that will set a diagnostic fault code. There is nothing to worry about, but it is a good idea to erase that code so it will not confuse someone in the near future. The only part of the circuit you are not testing this way is the sensor itself, but failures of temperature sensors is extremely uncommon because there is just one part inside them. Corroded connector terminals that add resistance to the circuit is more common than a failed sensor. That corrosion typically will not cause an incorrect temperature reading of just a few degrees. It is more likely you would see something around 100 to 150 degrees, and it is even more likely you would have an erratic idle speed tracking the erratic sensor readings.

The fans dont come till 222-228 depending on what the computer is programed to turn them on at. So if the temp didnt hit the correct temp the fan wont come on. If it didnt boil over thats a good sign. If you want to get a infared temp we can check and see how hot its getting etc.

You can get a pretty nice infared gun on amazon pretty cheap.I recommend a ray tech one I bought when they first came out.I have since like 1994 or 1995 and still works great.

Three cooling fan relays and an engine coolant temperature sensor are easiest and cheapest on the circuit that could cause this issue. If they have been checked/replaced already than all that is left is the power-train control module (PCM).

Hello,

I would try replacing the engine coolant temperature sensor which controls the fans via the PCM. Here is the fan wiring diagrams so you can see how the system works and the location of the sensor with a guide to show you the steps to replace it:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (below). Please let us know what happens.

Cheers

The fans come on at 225-230 in that car, does it overheat boil over? We should do a chemical check for the head gasket this guide can help us:

https://www.2carpros.com/articles/head-gasket-blown-test

Please run down this guide and report back.

The reason your gas mileage dropped is you disconnect the cts and it doesn't control the fans. plug it back in. There are 3 relays not 2 and 2 large fuses. they all must be checked. I'm including a diagram. If it's not a relay, then you'll have to have a pro check it for a bad connection or shorted wire coming from or to the pcm....

Heres a guide on checking relays and one on testing wiring, they will help you figure this out

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

https://www.2carpros.com/articles/how-to-check-wiring