Fans aren't turning off

[stefcio007]

When I leave the car and take the key out both fans start.
If I put the key back in both fans turn off.

The car can't be hot as it's a short trip and it's bloody cold outside.

Help.

[stefcio007]

Oddly enough when I opened the door and took my car charger out the fans turned off.
But I have noticed lately that the fans seemed to be running longer than usual after turning the car off.
Could it be just the charger I bought causing something? It only just started happening recently.

[stefcio007]

So still have this weird problem. Some kind of franken-fans.

[stefcio007]

They do turn off after a while, just odd why they even turn on in the first place even on such cold nights.

[stefcio007]

After 10 minutes they turn off, do I have a faulty sensor somewhere?

[stefcio007]

Replaced the 5A fuse that is part of the fan relay module because it was blown. No change.

[The_Hawk]

I had lots of fan issues with my VR6, I would mostly get high speed (and not the lower speed) and always had the thermo fans run after shut off, even though I didn't think they were needed.

After much screwing around I had a manual switch put in so I could turn them off:
http://www.vwwatercooled.com.au/forums/f47/thermo-fans-running-full-tilt-7162.html

Then I had AC issues and after a rebuilt compressor and a few new parts (receiver dryer and AC pressure switch) my thermo fan issues stopped.
http://www.vwwatercooled.com.au/forums/f47/air-conditioning-9758.html

Taken from that thread:

I stumbled across this info on another forum and emailed it to myself today, but forgot the link. Will update when I find it again.

In short it says that thermo fans staying on can be because of the pressure switch on the AC. Since my system currently has no gas in it, it may very well be that when it does the switch is causing my high speed to stay on... We will see very soon.

In response to "Why are my thermo fans always on"


For me, this turned out to be the AC pressure switch. It's located just below the AC Drier on the passenger side of the car, just under the front bumper. Mine was cracked and needed replacing. Once I did that, all was good again. You can remove the switch without discharging the AC system, so you may want to take it out and look to see if yours is damaged. If not, I'd say it could still be that because I epoxied mine and it didn't help. One other thing it could be is the thermostat...but I'm not sure on that one. Check the switch first, as it's easy to get to. If you have a Bentley, its on page 87-14. L8z




There are a bunch of sensors which can impact the fans (there are 3 or 4 temp sensors on that engine!) good luck!


(on a side note... Bitcoin???)

[stefcio007]

Thanks Hawk,
I'll check the sensors since that looks easiest to do and a sensor probably isn't too much.
It's little inconvenient when I park my car and the fans are roaring for 10 minutes. Can be heard from inside the house...

yeah, Bitcoin. I have a small solar array I built as a project and it's connected to some gear that generates Bitcoin that I then use on an EFTPOS card.
The address there is a donation kind of thing.

[The_Hawk]

It' taking me back a few year for those sensors, the ones one the rad and crack pipe you can change pretty easily, but remember that you're very likely to loose coolant in the process, so if you were ever thinking of a full flush, now's the time!

As for the AC sensor (which was my issue), I don't recall if that can come off while the gas system is under pressure or not. Mine was done *while* I was having half the system replaced so it wasn't an issue either way.


As for the bitcoin, Solar + bitcoin generator sounds interesting. Dedicated ASIC unit ticking away? Does it yield very much?
I played with bitcoin a little bit, but that was a long time ago now when GPU mining was still worth while.

[stefcio007]

Plugging out the blue sensor makes no difference.
Taking out the 20A control module fuse while the fans are running turns them off and when the fuse is plugged back in they stay off.

Not much, maybe a few dollars a month. Getting lots of batteries from faulty UPSes (taking the good ones) so making a big battery bank.

[Bug_racer]

There is a sensor on the radiator which has 3 wires . One is supply the other 2 send signals back to the fan ecu . You can start there , the 3 sensors in the thermostat housing I think only 1 has the power to activate the fan when it reaches 120 or so and it activates the super high speed fan .

[stefcio007]

There is a sensor on the radiator which has 3 wires . One is supply the other 2 send signals back to the fan ecu . You can start there , the 3 sensors in the thermostat housing I think only 1 has the power to activate the fan when it reaches 120 or so and it activates the super high speed fan .
Is that the one under the silver cyclinder canister thingy? I unplugged it and nothing changed if that helps.

[Bug_racer]

Its screwed into the radiator , its just above the lower coolant hose

[stefcio007]

I've got it, but not sure if taking it out will cause coolant to leak out.
Would the blown fuse have anything to do with it?
Which sensor should I replace first? And where can I get one.

[dylan8]

mine did odd things like this also.
Solved mine by tidying wiring and replacing just about every sensor in that department.
Sorry, cant be of more help

[Bug_racer]

I've got it, but not sure if taking it out will cause coolant to leak out.
Would the blown fuse have anything to do with it?
Which sensor should I replace first? And where can I get one.

Don't pull it out just check to see if there is power coming out of the switch

[stefcio007]

So, coolant is actually leaking from the sensor area, just booked it in to get it all sorted as I don't have time to do it all myself.

[The_Hawk]

Exploratory fixing on a car... that's not going to end well. I'd suggest they will remove the sensor, fix the leak and after that it's anyones guess.


To test a sensor you can either read it with a computer or a multimeter to see if it's reading correctly (and changing it's reading) as expected.

In this case, one of the other options is to plug in a spare (and known good) sensor and see what happens. Since the new sensor should be reading ambient temp the fans shouldn't come on. If they do, the problem is somewhere else.

Finding a random electrical problem is a bloody nightmare. It's a toss up between a good VAG specialist and an auto electrician who knowns VAG and it's likely to be long and expensive unless you get really lucky.

[stefcio007]

So, I was having a chat with my dad about buying a new Ford. And wouldn't you know it, the fans all work perfectly normal now!
I verified this a few times, just to be sure.
Going to buy new seals though to make sure I stop leaking, even though it's very minor.
here's hoping the issue doesn't re-appear.

[The_Hawk]

Have to wonder if it was loose wiring on one of the sensor causing the issue and all the fiddling as fixed them up!

[stefcio007]

Have to wonder if it was loose wiring on one of the sensor causing the issue and all the fiddling as fixed them up!
I think you might be right, it's gone bad again.
But I can't get any resistance from the brown sensor at all, might be on its way out? I'll be pulling them out tomorrow so that I can test them properly. Maybe the coolant has affected the wiring? Is it corrosive?

[stefcio007]

so, turns out the sensor was held in place using silicone and I also had a leak coming from the water pump.
All fixed now! :)

[stefcio007]

Sorry for bumping an old thread.
My "fix" for the fan issue had been to keep the 20A fan relay fuse removed because the issue eventually came back randomly.

Didn't know what the fuse was for and didn't appear to change anything when removed.
Today driving and wondering why the AC wasn't working. Turns out that fuse has to be in there otherwise it won't work.
Basically comes down to two things. AC sensor or fan relay module.

I don't mind the fan coming on during the hotter months since it "should" come on if it's hot, even if it isn't hot and it comes on, at least during summer it won't bug me when it happens.