I have replaced the Coolant Temperature Sensor (temperature switch) in my 1999 Ford Taurus. Today I was having a problem with the cooling fans not coming on, even after replacing the sensor. While the engine was running, I disconnected the wiring harness from the sensor. Checked the terminals with a volt meter, and the fans kicked on automaticly. One would think that it was simply because the cirucut was completed from the leads of the multimeter. Now here's the kicker. I plugged it back in, and the fans turned back off. Powered down the engine, and the coolant overflowed from the expansion tank. Went back out to the car to retest, and just disconnected the harness. Within a few seconds of disconnecting the harness, the fans kicked on at high speed. Nothing was touching the terminals of wiring harness. I plug it back into the sensor, and the fans switch off. Disconnect the harness again, and within just a few seconds, the fans kick back on at high speed. No power is being applied to the harness (nothing is plugged into it). How's this for a wierd car issue?
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Re: Here's a wierd cooling fan issue
Thats not too weird as the car would kick on the fans at full speed when it detects a problem with the sensor. Your ECU is not reading the sensor properly and needs to be checked by Ford. I hope this helps you.
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The cooling fan is controlled by the coolant temperature sensor near the thermostat, and when it senses too high temperature of the coolant, it operates the fan relay.
Check the fuse for the cooling fan, the cooling fan relay, and the fan itself for proper operation. You can use a multimeter to see if power is getting to the sensor. If not, and you find the fuse is good, then you'll have to find the break in the wire.
Change the sensor. Check the electric cooling fans and Relays. Some fans have 2 speeds and may not kick into high speed. The radiator operates more or less closely to the block temperature. A Laser thermometer would tell you what the operating temperature is.
With the switch on cross the 2 wires going to the coolant temperature sensor and if the fan comes on then replace the coolant tenp sensor.You check the fan relay by switching it with another with the same part on it in the fuse panel.
Replace the cooling fan relay switch. On the engine Coolant temperature Sensor make sure the sensor wire is still pluged into sensor and there is no damage to the wire in that area. If the wiring looks OK and was still pluged in then replace the Sensor. If you have allready figured out that the relay and the temperature sensor are OK. Key Off, then unplug the Cooling fan (near the fan) from the engine wirring harness.Run two wires from the fan plug directly to the battery, place one wire to one post the other wire to the other post. If the fan comes on then it is Ok if it does not come on then replace the Fan. Good Luck and have a good XMASS.
Jackie, Hi, yes this would be the problem if the temperature sensor is not working it will not tell the fan too start, so best advice would be too change this sensor, or have someone do it for you and that should cure your problem, Colin.
MOST OF THE TIME IF THE COOLING FAN FAILS TO OPERATE.THE COOLING FAN RELAY OR FUSE IS BAD.ALSO THE COOLANT TEMPERATURE SENSOR IS OPEN.THE COOLANT FAN WONT TURN ON.TO HELP YOU PIN POINT YOUR PROBLEM.GET IT SCAN.IT WILL TELL YOU IF THE COOLING FAN CIRCUIT IS WORKING OR YOU HAVE A BAD COOLANT TEMPERATURE SENSOR.YOU NEED THESE TWO COMPONENTS TO GET YOUR COOLING FAN TO OPERATE AUTOMATIC AGAIN.
The Taurus has Two temp sensors. One for the dash, which is isolated, then one for the PCM, it also controls when the fan relay should actuate. Its a 2 wire sensor, just above the thermostat. If you remove the harness from that sensor, and the cooling fan comes on, at any temp, (should take 5- 10 seconds) then thats your fault.
have u bled the cooling system ?warm the car and cut the car off right before the fans come on ,let sit for 30-35 minutes,see if the coolant drops in res. if so repeat process untill coolant stops droping ,then drive car regularly if overheating stops ,but monitor it because it will drop somemore/there has been reports of new and rebuilt water pumps nt having correct propelar mounted on them/ backwards etc. if this helps let me know email@example.com
You will overheat the engine if losing coolant.Firstly replace the cap with a new one,Is the engine temperature normal when you stop ? If its over temperature it will still blow out coolant. Check the radiator for blockage of the tubes & ensure the fan belts and water pump are in good order. Worst case is a blown head gasket can test for combustion gases in the coolant