Can I eliminate the radiator fan speed control module?

[Dake]

So in response to my own old thread, I now know my radiator fan speed controller is bad. Fan stays on all the time regardless of what coolant temp is reported. Okay. Given how you have to pull the front of the car off to get enough room, then hardwire in a new module, which is $$$, at very least I would want to make it removable using Weatherpacks or something so next time won't be as bad. But even easier than that, why can't I just splice a switch into the module's ground wire and manually turn on the fans whenever I drive the car? I've got cars with manual fuel pumps, manual fans, etc, so I'm not worried about forgetting or something, but I am worried about this module failing in some other way and suddenly the fans don't work at all. So secondary question I guess, why can't I just remove the module and wire up a manual fan switch? Or a more modern standalone fan speed controller?

Edit: Forgot to mention, I'm definitely being lazy but that's not the only reason. I'm also worried this part will one day be NLA as I've already seen evidence of its price going way up in recent years, supply going way down, and I have other vintage Audis where critical components are NLA.

[dreman78]

Yes you can, I bypassed my fan control module by installing relays to each fan and wiring them to individual switches.

[Kevin C]

The original fan controller lasted 20 years, assuming that you have new fans the chances of needing to touch it again are pretty low. The factory system works very well. If and when you cant get parts for it I would consider something different, I would just fix it.

[EuroxS4]

In theory you should be able to do it, however your going to have to find a way to turn the fans on(trigger). I would assume your gonna need a few relays and way to trigger/latch the relay to turn the fans on. Thats all the FCM is a bunch of relays that are latched once they get the signal to come on.

[Turbo510]

Latching relays stay 'latched' as long as there is power at the output terminal, or so I remember (except for magnetic latching types). The old Audi 5000 power windows used this for the 'one touch' down feature, and a thermal circuit breaker to turn it off. So, once on, would the fans stay on until the ignition is shut off with this arrangement?

When my daughter owned the 3.0, she had some overheating issues in traffic, because the fans were bad - opposite the OP's issue. However it might be interesting to use VCDS to output-test the cooling fan circuit, and check what happens at pin 3 of the FCM. The schematic shows one wire (Red/White) coming from the ECM. That could tell you if the FCM isn't responding to the ECM signal, or if the ECM signal is stuck.

[seanf86]

When my daughter owned the 3.0, she had some overheating issues in traffic, because the fans were bad - opposite the OP's issue. However it might be interesting to use VCDS to output-test the cooling fan circuit, and check what happens at pin 3 of the FCM. The schematic shows one wire (Red/White) coming from the ECM. That could tell you if the FCM isn't responding to the ECM signal, or if the ECM signal is stuck.

That wire from the ecm is a PWM signal. If the fcm doesn't see over a certain duty cycle within 10 seconds of ign on it defaults to full fan speed. I used a PWM controller to run the stock FCM in a 2.7t swap I did. I found that the mk5 vws used 25hz and a 10-90% duty cycle which works with the B6 module too.

[EuroxS4]

Theese FCM's are notorious for failing. When they fail, they run full blast wether it sees a signal or not and they don't care wether the car is running or if its closed and locked. Been there dealt with that shit in the past. Granted all of my B6 vehicle still having working FCM's I think onlyone vehicle was affected where I had to change the FCM however that car has over half a million miles on the clock and will be getting chopped in half soon.

[Kevin C]

FYI, most time the FCM is the victim of a worn out set of fans. I have 180,000 miles on mine and it still works perfectly. Even the ones that fail have lasted 15 to 20 years. I can deal with a part that fails every 20 years, when mine goes its just getting replaced.

[Gin+]

I'd just replace the FCM unless the car was a true beater. Ebay has knockoffs for around $50. Salvage yard would be even cheaper depending on your location.

[ImRobBailey]

I replaced my FCM with a junkyard part I pulled: $13.

[EuroxS4]

Personally I think I will be ditching the FCM when I have the engine swapped into my project. Most likely will be using 2 relays and pusher fans on the other side of the radiator as I need all the space I can get.

[walky_talky20]

I like the way the B5 (1.8T only) fan setup works. There's a "dual thermal fan switch" (not a sensor, just two thermal switches with 2 different thresholds in one package), and a relay each for High and Low speed.

No computers. No modules. Temp goes up, fan comes on. Temp goes up *more*, fan comes on *more*. It's simple and it works.

[EuroxS4]

I honestly think the B5 setup is so much better if you ask me. So I agree.

[ImRobBailey]

How difficult do you think it would be to retrofit a B5 fan control setup into a B6?

[Turbo510]

That setup pre-dates the B5 series by a long time too.