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Discussion Starter #1
Hi, I have done some searching on this, but with no success. 2001 Jetta GLS 2.0 AEG. The cooling fans are staying on after you turn the key to on then back off. I understand it will do that when it is hot after shutting off the car, but it will do it cold too. They stayed on until the battery was dead. I can go out in the morning and turn the key to on, (not started) and the both fans will come on. How long shoulld I expect them to stay on? 5, 10, 15 min? If I disconnect the battery cable and immediatly re-connect it the fans will stay off. I had replaced the relay located under the battery tray already with no change. I also unplugged the temp sensor plug located on the radiator with no change. I was thinking with that unplugged the fans should stay off. Is that a correct assumption or should I be looking to change that too? Thanks for the help!
 

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Sounds like fan control module.


VWVortex.com - How to test Rad. Fan control Module, or have fans run on high
1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
5. If the fans run as described in steps 3 and 4, it indicates that the cooling fans and circuits are running properly and the thermo switch is faulty.
6. If the fans do not operate with the thermo switch bypassed, check for voltage at the red wire of the thermo switch electrical connector. There should be battery voltage.
7. If voltage is not present check the large cooling fuses in the engine compartment fuse holder and the No. 16 fuse in the passenger compartment fuse box. If the fuses are OK, the problem lies in the wiring harness, the fan control module or the coolant temperature sensor.
8. Check the wiring for open or short circuits. The fan control module can only be diagnosed as faulty through process of elimination.
 

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Discussion Starter #4
Sounds like fan control module.


VWVortex.com - How to test Rad. Fan control Module, or have fans run on high
1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
5. If the fans run as described in steps 3 and 4, it indicates that the cooling fans and circuits are running properly and the thermo switch is faulty.
6. If the fans do not operate with the thermo switch bypassed, check for voltage at the red wire of the thermo switch electrical connector. There should be battery voltage.
7. If voltage is not present check the large cooling fuses in the engine compartment fuse holder and the No. 16 fuse in the passenger compartment fuse box. If the fuses are OK, the problem lies in the wiring harness, the fan control module or the coolant temperature sensor.
8. Check the wiring for open or short circuits. The fan control module can only be diagnosed as faulty through process of elimination.


Thanks Shameless!
When I can play with it again, I will try the jumper wire test to see if the fans change speeds when jumping the different terminals. I had that unplugged once while troubleshooting and both fans still came on high without jumpers when the key was turned on. Should they have?
I had already replaced the fan control module without any change.
I replaced the coolant temperature sensor today that a mechanic friend said to give a whirl, but also no change.
The cooling fan switch (easiest & cheapest next step) is I guess the last thing to try before chasing wires looking for a short or could it be a bad ecm?
Thanks again for thoughts or help!
 

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Discussion Starter #5
Thanks to all that gave ideas or tips to try and get this fan issue straightened out. I just wanted to drop a note to say what I finally found to be the problem. To make a long troubleshooting process short......With the warm weather I found that the AC compressor clutch wasn't getting power either. I started chasing wires and found one of the wires in the FCM wire bundle that was hidden by covering had corroded and broke. Reconnected it, AC clutch and fans now working normally again!
 
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