Cooling Fans - Troubleshooting Assistance

[Ian W]

Hi!

After some advice in getting to the bottom of my cooling fan issues (aka they don't work).

I've checked the fuses on top of the battery, they all look good.

I puled fuse 16 and fan on the drivers side spun into life, the other moves freely but nothing happened with it. Does that suggest my control module has packed up?

What would be my next test? I've read something about applying 12v to the fan switch? Is that correct? Can anyone supply more detail?

TIA Ian

 

[s3mad_dude]

I think the second fan comes on when the A/C is active. Try turning that on. And see if that makes a difference. I haven’t got my S3 with me so I can’t check.

You could apply 12v from a battery to the power terminals to see if it spins up or you could check with a multimeter if you have continuity. That would give you the confidence that the part works, and then perhaps your problem lies elsewhere with the car not telling the fan it needs to come on (if that makes sense?)

 

[Ian W]

I think the second fan comes on when the A/C is active. Try turning that on. And see if that makes a difference. I haven’t got my S3 with me so I can’t check.

You could apply 12v from a battery to the power terminals to see if it spins up or you could check with a multimeter if you have continuity. That would give you the confidence that the part works, and then perhaps your problem lies elsewhere with the car not telling the fan it needs to come on (if that makes sense?)

Thanks, I am hoping to try the fans with a direct 12v this weekend, as you say, that should tell me if it is a worn out fan or something else (or both!)

The small fan spins when I removed fuse 16, this is the aircon fan I believe but under normal condition, when I switch on the aircon, the fan doesn't spin up so it may well be the fan controller. Wouldn't surprise me to find a couple of issue, it is 22 years old now after all

 

[Rainbird]

I was under the impression both fans should come on together, rather than one at a time.

AC on should induce slow speed regardless of engine state. 95 and 102 degrees* coolant temp to trigger slow and fast speed respectively (*typically, some rad switches had different trigger points).

You can test the fans themselves by disconnecting the connectors and applying 12v directly to pairs of pins. One pair will do slow, one will do fast. Test each fan to confirm if everything is working as it should.

CTS and the rad switch are cheap and easy to replace if it comes to it, plus you can pull them out and test in hot water if you really want to.

FCM is trickier to diagnose than the above, so I'd start with that lot and if it's still not working, drop in another FCM and see if it makes the difference

 

[Ian W]

Yes, I agree, I can force the small fan on but I believe they should both spin up which leads me to believe the bigger one is dead, I will confirm that though by giving it the 12v test.

AC does nothing to the fans which is what makes me think it could be the control module but hopefully I will have a clearer picture after this weekend. Assuming I will be replacing the bigger fan in the coming weeks, I will do the rad switch at the same time, and as you say, the CTS as well probably.

Thanks

 

[Ian W]

Bit of progress today..

So went for a drive then let the car idle, temp got to about 95 and the smaller fan kicked in (i assume this was low speed), car never got hot enough to use high speed.

Then I started to remove bit to get to the connectors, removed the plug from the rad switch and was able to get the small fan to run on demand, again, larger fan does nothing.

Wasn't able to release the connectors for the fans to test independently from the top of the car but will get under it tomorrow and hopefully I can confirm my suspicions that the larger fan is dead.

So that leads me to the question, can I replace just the large fan? Any links to a replacement? Will I have to remove the entire assembly or can I remove just the fan and swap out?

Oh, and is the fan assembly on a 225 TT the same?

Thanks

Ian

 

[Ian W]

A bit more troubleshooting yesterday, I applied 12v to both fans, the smaller one only has one speed working, the larger one is dead and won't do anything.

So, look like I have my answer, two new fans please! Can't say I am looking forward to this job!

 

[AGB-S3]

Could have the same problem

Engine Idle . no fans . then when hot small fan starts , gauge never shows more than 90
no sign of the large fan running
air-con brings the driver side on only

Q what controls the two fans ? Radiator switch, and FCM - fan control module ? - where located ?

Tnx-G

 

[hydro s3]

The way I understand the way the fans work is that: Car running and when hot big fan kicks in then if you turn on the air con the wee one starts.

 

[AGB-S3]

The way I understand the way the fans work is that: Car running and when hot big fan kicks in then if you turn on the air con the wee one starts.

Tnx , I think, I have lost the near side fan, not rotating, when hot the off side fan started and stopped
air-con on the off-side fan only runs

 

[AGB-S3]

Car Registration number , Radiator temp switch has TWO part numbers , each 3 pin ..
Q What is the difference ?

 

[Ian W]

The way I understand the way the fans work is that: Car running and when hot big fan kicks in then if you turn on the air con the wee one starts.

Isn't it...

Switch air con on - small fan runs

When coolant reaches a certain temp, both fans come on at low speed, if coolant doesn't come down in temp, both fans kick in to high speed.

 

[hydro s3]

@Ian W O not sure on that. I was just going on the way I thought mine went. You could well be right.

 

[Ian W]

@Ian W O not sure on that. I was just going on the way I thought mine went. You could well be right.

I'm pretty sure that is it, done quite a lot of testing with mine the last few weeks, hopefully won't be long until I have them both replaced!

 

[AGB-S3]

Removing the cooling fan's mounted on plate-
How ? will it lift out from the TOP as complete assembly
or need to remove other items first ??
Tnx-G