x-type cooling fans not working RESOLVED
#21
05-23-2021, 08:10 PM
Well today was takeing care of some things on my 2002 x-type and seen that the fans are not coming on has any one had this problem checked all fuses and relay i have a very great guy that works on my car so im trying to see the fix for my jag.
any help will be very good.
any help will be very good.
#22
05-23-2021, 11:39 PM
Veteran Member
Hello TheTerrible Keleb,
Let's hope the fan controller is OK, that it is just being tricked into turning the fans on hard.
The fan control module is activated and speed controlled via the ECM (Engine Control Module), so the ECM decides on when to call the fans on and what speed to run them at.
Normally you should find that as engine heats up, the FCM (Fan Control Module) will likely turn only one fan on initially and if engine needs more cooling the FCM will increase fan speed until it then brings second fan on as well.
The ECU is monitoring sensor inputs from both the ECT (Engine Coolant Temperature) sensor and the EOT (Engine Oil Temperature) to decide if and how much fan cooling is required.
If either sensor is faulty, the ECM may be instructing the fan controller to turn on immediately and run at full speed.
Check these sensors for correct voltage measurements; with a cold engine they should have around 5V across the sensor and as engine warms the voltage will decrease getting lower towards zero volts.
If you have very low voltage on a sensor with a cold engine, briefly unplug sensor to see if fan stops. If so, then replace the suspect sensor.
Note: there is also a fluid temperature sensor in the transmission that is reporting in the same way into the TCM (Transmission Control Module) that will also talk to the ECM and bring fans on.
So if it is not the ECT or EOT sensor on the engine, it may be a false reading from the transmission temp sensor.
If all sensors read properly then it may be the Fan Control Module has short circuited inside and just powering fans on regardless of input from ECM.
Hope this helps with some diagnostic steps for you.
Let's hope the fan controller is OK, that it is just being tricked into turning the fans on hard.
The fan control module is activated and speed controlled via the ECM (Engine Control Module), so the ECM decides on when to call the fans on and what speed to run them at.
Normally you should find that as engine heats up, the FCM (Fan Control Module) will likely turn only one fan on initially and if engine needs more cooling the FCM will increase fan speed until it then brings second fan on as well.
The ECU is monitoring sensor inputs from both the ECT (Engine Coolant Temperature) sensor and the EOT (Engine Oil Temperature) to decide if and how much fan cooling is required.
If either sensor is faulty, the ECM may be instructing the fan controller to turn on immediately and run at full speed.
Check these sensors for correct voltage measurements; with a cold engine they should have around 5V across the sensor and as engine warms the voltage will decrease getting lower towards zero volts.
If you have very low voltage on a sensor with a cold engine, briefly unplug sensor to see if fan stops. If so, then replace the suspect sensor.
Note: there is also a fluid temperature sensor in the transmission that is reporting in the same way into the TCM (Transmission Control Module) that will also talk to the ECM and bring fans on.
So if it is not the ECT or EOT sensor on the engine, it may be a false reading from the transmission temp sensor.
If all sensors read properly then it may be the Fan Control Module has short circuited inside and just powering fans on regardless of input from ECM.
Hope this helps with some diagnostic steps for you.
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