My radiator fans are (not) coming on....

Type_R · 20 Apr 2013 at 13:47

Car: MK5 Golf GTi

I have noticed for a few weeks that the rad fans have not been working. I thought it was the bad weather and a faulty ECT sensor, which I replaced last week. The coolant temps are now absolutely fine but neither of my rad fans are ever on.

So I took out VCDS, used Engine > output tests > Fan 1 control - both fans spun up in unison like they should so they are working fine.

I then turned on the Climatronic A/C - apparently the small fan should start spinning when the Air con fires up. The air con is blowing relatively cold air, VCDS is reporting no faults with the Air Con system, compressor seems to be starting up - reported as ON in VCDS, yet my rad fan never turns on, even after a long drive.

So the fans are working, the air con compressor is working, what gives?

Chris1712 · 20 Apr 2013 at 13:52

It's not hot enough to need to turn them on? Surely.

Type_R · 20 Apr 2013 at 13:54

Chris1712 said:
It's not hot enough to need to turn them on? Surely.

That might be the case with engine cooling, but apparently the Golf utilises the small rad fan to cool the A/C system and should therefore come on when the compressor starts.

[TW]Fox · 20 Apr 2013 at 14:13

The airconditioning system in my car only runs the electric fan when system pressure reaches a certain level. It is therefore not on all the time. Perhaps yours is similar?

paradigm · 20 Apr 2013 at 14:15

Sounds like a blown resistor pack in the fans.

I had the same in my MK1 leon, and ended up adding my own external resistor pack. Worked a treat, even if it did look a bit ghetto. Better than the fortune Seat/VW wanted for a replacement set of fans though!

[TW]Fox;24151080 said:
The airconditioning system in my car only runs the electric fan when system pressure reaches a certain level. It is therefore not on all the time. Perhaps yours is similar?

Nope. The fans run at a slow speed when the aircon is turned on.

Type_R · 20 Apr 2013 at 14:24

paradigm said:
Sounds like a blown resistor pack in the fans.

I had the same in my MK1 leon, and ended up adding my own external resistor pack. Worked a treat, even if it did look a bit ghetto. Better than the fortune Seat/VW wanted for a replacement set of fans though!

Strange though that when tested with VCDS they perform perfectly and spin up on command!

How did you go about attaching your own resistor?

paradigm · 20 Apr 2013 at 16:42

The fans will both still run at 100%, but they won't run at the lower speed if the resistors are shot. No faults were ever logged on my VCDS either.

I followed this guide:

http://www.seatcupra.net/forums/showthread.php?t=331943

Type_R · 20 Apr 2013 at 16:56

paradigm said:
The fans will both still run at 100%, but they won't run at the lower speed if the resistors are shot. No faults were ever logged on my VCDS either.

I followed this guide:

http://www.seatcupra.net/forums/showthread.php?t=331943

When I test them with VCDS they start off slow and then speed up before slowing down again. I'll check out the guide thanks.

Dangerous Dave · 20 Apr 2013 at 17:45

The fan system on the MK5 Golf isn't the same as the MK4 Golf/MK1 Leon, I noticed that my fans weren't coming on with the aircon yesterday on my MK5 Golf, not had a chance to check further but will be this week. I can't recall from previous years if this was the case when it was just over the 4c cutoff limit.

Minstadave · 20 Apr 2013 at 18:01

Mine have never come on, well I've never heard them on my 2005 A3 2.0T, it's survived 60k miles in three years so I'm not worried.

Type_R · 20 Apr 2013 at 18:09

Just sorted it! Opened the fuse box in the engine bay! Noted fuse F38 (rad fan fuse for GTI) was inserted the wrong way (don't know if it makes a difference!). Took it out and put it back in the right way up! Turned on A/C and the fans fire up at low speed

!!!

Dangerous Dave · 20 Apr 2013 at 20:28

Pulling the fuse and putting it back in sorted mine aswell :-)

, do both your fans spin up with the aircon ? I always thought it was only the smaller fan but both of mine are coming on.

The direction of the fuse doesn't matter so it must just be killing the power to a control module and resetting it, my aircon hasn't been on since November for any great length of time due to it being under 4c so this may have caused a problem.

Type_R · 20 Apr 2013 at 20:32

Dangerous Dave said:
Pulling the fuse and putting it back in sorted mine aswell , do both your fans spin up with the aircon ? I always thought it was only the smaller fan but both of mine are coming on.

The direction of the fuse doesn't matter so it must just be killing the power to a control module and resetting it, my aircon hasn't been on since November for any great length of time due to it being under 4c so this may have caused a problem.

Yeah both of mine are coming on at 'low speed'

Dangerous Dave · 20 Apr 2013 at 21:06

Mine have stopped working again after another drive, I will need to look into it more. The system may work like Fox is suggesting as it is only 6c at the moment.

Type_R · 20 Apr 2013 at 21:10

Dangerous Dave said:
Mine have stopped working again after another drive, I will need to look into it more. The system may work like Fox is suggesting as it is only 6c at the moment.

When I tested them earlier today the outside temp was 12C and they were not working. After taking out and putting in the fuse, they were working fine. I'll try mine again in the morning when it is cold to see if they still run.

Dangerous Dave · 20 Apr 2013 at 21:16

Type_R said:
When I tested them earlier today the outside temp was 12C and they were not working. After taking out and putting in the fuse, they were working fine. I'll try mine again in the morning when it is cold to see if they still run.

It was 6c when they were working after pulling the fuse 30 minutes later after a quick trip they were off again but the aircon compressor was still engaged.

Jono8 · 20 Apr 2013 at 22:25

If your air con is working fine, and your car isnt overheating.....what is the problem?

Type_R · 20 Apr 2013 at 22:26

Jono8 said:
If your air con is working fine, and your car isnt overheating.....what is the problem?

They are not working to specification

That is the problem

Jono8 · 20 Apr 2013 at 22:52

Type_R said:
They are not working to specification That is the problem

Do you have the specification in front of you that clearly states - "small rad fan will always be on at any time that the air con is on" ?

Type_R · 21 Apr 2013 at 09:26

Jono8 said:
Do you have the specification in front of you that clearly states - "small rad fan will always be on at any time that the air con is on" ?

In a word - Yes