How do you test a radiator fan control module with a multimeter?

Pusrant to my other thread I think i have determined my rad. fans are only running on low. Before I go and drop the $$ for a new control module can anyone tell me how to test the module or make the fans run on high. Or for that matter can someone tell me what tells them to kick into high. They come one when the a/c is on but on on low and I have never heard them on high and living in Texas it should have happened by now.
Car in question is a 2002 Jetta wagon, 1.8t. Unfortunately I don't think the module on my MKIII is the same so I can't just do a swap test.
If there is an easy way to make them run on high all the time that would also work for now till I can get a new module, provided that is the problem.

Re: How to test Rad. Fan control Module, or have fans run on high (jsbaker)

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.

having this issue with my TT. The fans only seem to come on occasionally when the car has been turned off...But never come on when the car is running hot and still running....So i know the fans work, but didn't know what else to look into...

Thanks for the info...:thumbup:

I was wondering were this thread was hiding. I'm glad it was helpful!

:beer:

Excellent thread.

I have disconnected the wire from the radiator temperature sensor.............and the fans CONTINUE running. wtf? I am guessing fan control module is gone. Will be performing the tests as described above tomorrow and see what happens.

I have this problem but kind of different. my auxiliary fan for the radiator is not turning on when I turn on the a/c on all the speed settings. but, i could see the a/c compressor turn on. would this be a fan control module problem? the part# i checked for my car, this is what I will need, 1J0919506K.

any help will be great. thank you.

Excellent thread.

I have disconnected the wire from the radiator temperature sensor.............and the fans CONTINUE running. wtf? I am guessing fan control module is gone. Will be performing the tests as described above tomorrow and see what happens.

Thank you for the info. I used this to test the low speed and high speed last night. ended up that the low speed does not turn on on both of them. I am finally concluding that the 2 of my auxiliary fan is bad.
A/C smaller fan part# 1C0959455C (female connector)
Engine bigger fan part# 1J0959455S (male connector)

I have this problem but kind of different. my auxiliary fan for the radiator is not turning on when I turn on the a/c on all the speed settings. but, i could see the a/c compressor turn on. would this be a fan control module problem? the part# i checked for my car, this is what I will need, 1J0919506K.

any help will be great. thank you.

have you tested your fan if it's running on high per the instruction here?

Pusrant to my other thread I think i have determined my rad. fans are only running on low. Before I go and drop the $$ for a new control module can anyone tell me how to test the module or make the fans run on high. Or for that matter can someone tell me what tells them to kick into high. They come one when the a/c is on but on on low and I have never heard them on high and living in Texas it should have happened by now.
Car in question is a 2002 Jetta wagon, 1.8t. Unfortunately I don't think the module on my MKIII is the same so I can't just do a swap test.
If there is an easy way to make them run on high all the time that would also work for now till I can get a new module, provided that is the problem.

How to Test the Fan Control Module

"On this vehicle, the cooling fan and A/C compressor operation are controlled by the J293 fan control module, which is usually located in the driver's front corner of the engine compartment on the lower frame rail. The J293 module has both a 14-pin connector identified as the T14 connector in Volkswagen wiring diagrams and a four-pin connector identified as the T4a connector. To diagnose this system, starting on the T14 connector:

1) Start and idle the vehicle. Select "A/C on" at maximum cooling and "blower on" at high speed.

2) Check for 12 volts at the T14 connector pin No. 8 (T14/8). This 12-volt signal comes from the A/C switch and requires both cooling fans on at low speed and compressor activation.

3) Check for 12 volts at pin T14/9. This voltage is a switched ignition source and will have 12 volts when the ignition is in the "on" position.

4) Check for 12 volts at pin T14/4. This is a constant battery source and should read 12 volts at all times from fuse S16.

5) Check for a good ground at pin T14/6.

6) Check for 12 volts at all times at the four-pin connector, T4a pins T4a/1 and T4a/3 from fuses S164 and S180, respectively.

7) Turn off the ignition. Remove the T14 connector and check for continuity between pins T14/14 and T14/5 on harness side to ensure proper operation of the F38 ambient temperature switch. Continuity must be present if the ambient air temperature is above 32 degrees Fahrenheit. Reconnect the T14 connector and restart the vehicle.

8) Check pin T14/2 using a duty cycle meter. If the refrigerant charge in the system is normal, about 30 percent to 35 percent duty should be indicated at pin T14/2 without the compressor engaged. The duty cycle signal is supplied by the G65 pressure sensor in response to system pressure changes. A duty cycle above 90 percent or below 20 percent will command the compressor off.

9) Check for an 11-volt reference voltage at pin T14/3. The reference voltage originates in the J293 fan control module and can be grounded by |the power control module (PCM) under certain circumstances (typically wide open throttle or vehicle overheat conditions) to turn the A/C compressor off.

If zero volts are present, the PCM is commanding "compressor off" or the wiring harness is shorted to ground. Raise vehicle idle speed above 2500 rpm and observe compressor operation and voltage at pin T14/3. If the voltage at pin T14/3 returns to 11 volts with the idle speed above 2500 rpm and compressor operation resumes, then a throttle basic setting procedure is needed and must be performed with a factory-compatible, by-directional scan tool. Note: A loss of throttle basic settings will keep the compressor from activating.

If all previous tests have passed, check the T14 connector pin T14/10 for 12 volts. This pin is the output signal to the compressor clutch coil. If all the other tests have passed and there is no voltage at pin T14/10, this indicates a faulty fan control module."

I got this from this link... //www.gti-vr6.net/wiki/index.php?title=Fault_diagnosis_in_the_Fan_Control_Module

have you tested your fan if it's running on high per the instruction here?

Trying this out tomorrow.....hope it solves my problem:facepalm:

valuable info, thank u for the thread!!

Ive had overheating issues, and fans not working, along with my AC coming out warm! I started by changing out the coolant temp sensor, and than tested the fans which were dead! Since than Ive replaced coolant temp sensor which turned my AC cold again, but fans still dont kick in when overheating unless I turn AC on?! They have been cutting in n out and NOW after reading this thread, Im hoping to get to the bottom of this!!

Thanks again for such a detailed thread!!

is it possible for the fcm to fail intermittently? how does the cts affect the fans?

does anyone have a pic where to fan module is? Im pretty sure mine needs replacement.

The FCM is basically underneath the battery. You can't miss it!

It looks like this:

The FCM is basically underneath the battery. You can't miss it!

It looks like this:

:thumbup::thumbup::thumbup::thumbup::thumbup::beer:

fyi, in 8 years I have never replaced a Fan module on a mk4.

I have though replaced probably 20 fans, and probably 20-30 fuse/relay pannels on top the battery related to radiator fan issues.

I only needed to replace mine because when I got rear ended it pushed me into the tow hitch of the Eurovan in front of me. Guess where it hit...