My cooling fan does not come on--I saw the temp gauge show a rapid increase yesterday. When I got the vehicle home I realized the fan was not running. It usually does for a short while after I turn the car off. The fan rotates freely and is not jammed or off-center. I checked the fuse and it is not blown. I realize it could be the relay, resistor,sensor, or fan motor, I know where the relay and motor are, don't know where the resistor is. Anything would be appreciated.

is the cooling fan cutting in ? run the engine whilst stationary with the hood up , give it a little gas 2000revs and wait for the temp gauge to rise ,the cooling fan should be heard cutting in , and off again once cooled the engine temp down ,this may take 10-15 mins but you have to be sure the fan is cutting in or you may cook the engine

Coolant temp sensor...

Vehicle temperature gauges (temp gauge) read the temperature of the liquid in cooling system. From what I understand, the temp gauge jumping around has since gone away after you placed water into the radiator. It is very possible that water converted into steam was trapped in the cooling system and reached the temp sensor in your engine. The vehicle moving caused this steam to shift around reflecting rapid changes in temperature on the sensor, causing the needle to jump around on your console.
Hope this helps.

If the temp gauge shows normal, you would not expect the fan to be on much. It is controlled by the coolant temp sensor. If the fan will not come on when the car gets really hot, it is possible this sensor has failed.

It is normal for both AC and cooling fans to be on when you turn on AC to cool setting.

Very correct the ECT is a 2 wire thermistor,when coolant temp increases, the resistance andsignal voltage decrease,If you disconnect the sensor the fan goes on, you just trouble shooted the vehicle cooling fan switch, If anything the signal to the gauge itself may be non-op and not getting to the indicator, try this with vehicle at warm up temperature if you turn the A/C does the fan turn on.it should if it doesnt the power juction box (fuse and relay in engine compartment should be checked, for any opeen fuses, By the way the guage information is from the PCM

The fan staying on for a few minutes wass just the fan and sensor trying to bring the temp down at the radiator.

As for the AC shutoff warning, you may not have enough coolant to keep the engine cool. With the engine off and cold, check the radiator and the overflow jug, ensuring they both have the proper amount of coolant. If either is low, fill to specs and drive the vehicle to see if it stays cool. If filling them doesn't fix the problem, you may have a stuck thermostat.

When the engine was running hot, did you notice if the fan was running or not? If it was not, then you may have a fan sensor going out. If it was, you may have a low coolant or thermostat problem

Probably a cooling fan issue or maybe a stuck thermostat.. change thermostat and check that cooling fans engage..good luck...also when you fill up the resorvoir let it be for a while and check to see if level is down, sometimes it takes a while for water to seep into radiator, i assume you dont have a radiator cap?

Terry, what's happening, is when you turn your heater on, no matter what temp you have it set at, the vehicle allows coolant to pass through your heater core, and the blower motor acts as another cooling device for the anti-freeze. The next steps I would take, is to check your fans. Let the vehicle warm up a bit, and look under the hood and see if they are turning on at all. If they are, next, you may need to flush your entire cooling system. First start with the radiator, and if that does not help, you may need to flush the entire system, which flushes water jackets throughout the engine, AND the radiator at the same time. Now, if you are not seeing bubbles, (check under the radiator cap also), I would doubt it is a crack anywhere. Take the first steps I gave you, and see if this fixes the problem. Hope it helped you out.

Well, it can be a sending unit issue, they are pretty inexpensive, so worth while to just replace it. Do be aware that the temprature DOES normally do what you describe. The condition is called heat soak, where the temp goes pretty high, due to no water circulation, after shutdown. This is normal and some vehicles run fans after shutdown to help. Usually not an issue with properly functioning cooling system that can hold pressure.

Remember the coolant recovery tanks? Their purpose was to recover teh small amount of coolant pushed out during heat soak.

Check the cooling fan switch. It appears your auxiliary electric cooling fan isn't going on when at idle. and engine temp increases. While you are driving, air is being rammed thru your radiator as you cruise along, so it isn't overheating, at idle, that isn't happening, and the fan should go on as the temp goes up. When the ac is switched on, the fan is being signaled to operate due to the heavy ac load on the cooling system.