Mechanics

COOLING FANS WONT COME ON

2001 Chrysler Sebring

Engine Cooling problem
2001 Chrysler Sebring 6 cyl Two Wheel Drive Automatic 86,000 miles

I have a 2001 sebring LXI 3.0L V6 Coupe, my cooling fans work when I turn compressor on and engine is fine I can hear the high speed fan kick in and all is good. When the fans are off and the motor reaches operating temperature the fans wont kick in, and the gauge starts to rise. I have changed the relay, themostat and temperature sensor. And nothing seems to solve this problem. There is a sensor by the front of the radiator that is closed ended. I dont know what it is but it just sits there. Did I mention its a mitsu motor. I hope some one out there knows this motor and can help its only in 17% of cars. Please help thank you.
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Shantigeary30
April 16, 2009.




Unplug your new sensor while the engine is running. If the fans turn on when you do that, they're working correctly. If the fans do not turn on, check the temperature gauge in the dash. If it went to full cold, you replaced the wrong sensor. The sensor for the engine computer which runs the fan relay, and the sensor for the gauge are two different sensors.

Caradiodoc

Caradiodoc
Apr 19, 2009.
The two sensors are different size, the temperature sensor is the froward sensor and the small one behind it is the gauge sensor which is on the motor not the dash. If the gauge sensor was bad would it be reading anything at all? Would that affect the fan coming on at all? The temp sensor works cause when the ac/heat switch is on, the fans run and I can hear it kick in when the engine reaches op temp. But when I dont have the ac/heat running then nothing runs and the car gets hot, has not over heated yet but it goes above the op temp

Tiny
Shantigeary30
Apr 19, 2009.
It is extremely rare for the gauge's temp. Sensor to fail. If the resistance value is off a little, the gauge will just read a little high or low. Problems occur when someone installs the sensor with teflon tape around the threads to insure a good seal. Most of these sensors use a single wire. The second wire is the threaded body. Teflon tape can insulate the sensor and the gauge will stay on full cold. Another problem is bent and stretched pins in the connector.

All kinds of new problems are showing up on newer cars because instead of simple mechanical gauges, instrument clusters are unreliable computer modules that run the gauges which are just voltmeters. Information is passed through the body computer, then sent to the cluster. Since computers over-complicate the circuitry, gauges are giving a lot more problems than in the past. Nevertheless, the gauge circuitry is completely independent of the computer controls that affect engine performance.

Temp sensors for the engine computer always have two wires. Rather than using the brass threads for the ground connection, the ground wire goes back through the computer so it can monitor current flow. These sensors have caused a lot of problems on Fords, but not on other car brands. If anything causes an open circuit, such as unplugging it, the computer won't know actual engine temperature, so the it will command the radiator fan on in case the engine is overheating. On older cars, this also killed any electronic timing advance. It was common practice to unplug the sensor when setting base ignition timing with a distributor when doing a tune-up.

Under normal conditions, the engine computer turns the radiator fan relay on at 210 or 212 degrees, and off at 198 degrees. In addition, the computer will command the relay on whenever the air conditioning is turned on because of the extra heat load presented by the condenser which sits in front of the radiator. On some models, the fan runs constantly with the AC on. On some models, the compressor cycles on and off, and the fan cycles on and off at the same time. This cycling has nothing to do with engine coolant temperature. It is in anticipation of the condenser temperature.

The engine computer performs a check on the coolant temp sensor when the engine is cold. It expects the temperature to be the same as the ambient air temp sensor or the battery temp sensor. If significant disagreement is found, the computer may memorize a diagnostic fault code and turn on the " Check Engine" light. This is a pretty rare occurrence.

Hope that clarifies the fan operation. The AC and the temp sensor are two different circuits that independently affect when the radiator fan runs. Your mechanic can connect a hand-held computer that will read out the sensor values the engine computer sees. You can watch coolant temperature rise as the engine warms up. This is the sensor that affects fuel metering and emissions, but it has nothing to do with the gauge.

Caradiodoc
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Caradiodoc
Apr 20, 2009.

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