Radiator fan not functioning. How best to test?

[Ben Cordy]

Hi all i've got a 3 cylinder 1.2htp. Went to get the aircon serviced today and unfortunately discovered I wouldn't work due to the cooling fan not functioning. I've never noticed the fan function even when the cars been running hot but as it never actually overheated I didn't look into it.

The aircon guys only discovered as it wasn't cooling as much as it ought. I've connected the fan directly to the battery and it spins perfectly and the fuses are all perfect. I assume it has a relay or switch somewhere but where?

What's be best steps to test the switch and track the problem? Most the info out there seems to be for the 1.4mpi but obviously this is a different arrangement!

Any help well appreciated!

[Breezy_Pete]

Not sure which fan you mean, but if you mean the main one, rather than the smaller one that only comes on with the aircon, then see below.

 

Haven't had any dealings with the system on ours, but it looks like there's a dual thermoswitch in the radiator, just above the bottom hose.  See diag and temperature info here. 

Thermoswitch connector will have three terminals, and bridging the common one to each of the others should bring the  main fan on at its two speeds. If this works, the thermoswitch itself may be knackered.  Looking at ours just now, seems there's a brown wire and two others. I bet the brown wire is ground (0V) and bridging this to the others one at a time will simulate the radiator being hot enough to trigger each of the two fan speeds.

Access doesn't look brilliant to unplug the connector unfortunately.

 

There appears to be a 'control unit' (presumably containing relays) hanging off the chassis leg just adjacent to the thermoswitch, and if this 'bridging test' doesn't give expected results, that unit is likely to be the problem.

 

Good luck. (Edit: Oh, don't forget to turn ignition on before bridging tests, and make sure all bodily parts are clear of where the fan will spin before bridging!)

[Ben Cordy]

That's brilliant! Thanks for that. In the morning I'll have to test like you've suggested although looking through I've spotted a fairly elementary issue....namely the lack of a second fan. Mines only got the one large fan which I noticed has only 2 wirrs on the harness where the connection to the cars loom has 3. I'm aware the car had a frontal impact at some point I'm guessing it's been replaced with a more readily available single fan from a non ac model.

Am I right to say all ac cars should have dual fans? If so do they run off a single wiring connector as I haven't seen a second unused anywhere around that part of the engine bay.

[del-gti]

I know I've answered your other post but thought I'd post here too.

As far as I know, a/c cars can have just one fan - like mine. The fan controller regulates the speed. I.e. switch on the a/c, fan runs at low speed. Engine gets too hot, fan runs at fast speed.

As I mentioned in my other post, my fan doesn't run at low speed when the a/c is switched on. I'm pretty sure this is due to a defective fan controller.

[Ben Cordy]

Thanks for the replies on both counts! Think mine is probably a similar issue although in the process of trying to diagnose the issue I discovered a big gash on the radiator hose.... Unfortunately looks like I'll be getting a few bits done once I get back from my holiday!

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[Ben Cordy]

Well thanks again for all the help. After telling the mechanic that I'd never had any issues with the car overheating (hence my surprise at that being the ac issue!) I spent a good bit of time in the hard shoulder of the motorway this weekend with an over heating engine! 

 

Thankfully it's booking into the garage tomorrow however from my explorations the fan controller looks to be at fault (fan runs when connected directly into the battery but not when bridging the fan temp sensor connector.) 

 

Hoping to avoid a big bill but will have to see how things go! All coming together at once!

[Holmesie]

if its expensive you could always put a switch and fuse in and wire it to the battery to cure your over heating issue 

[Ben Cordy]

if its expensive you could always put a switch and fuse in and wire it to the battery to cure your over heating issue

Thought about that. Think I'm just going to fork out on this occasion, added benefit of providing working air con!

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[Breezy_Pete]

You have checked the fuses above the battery, have you?  There appears to be a 40A in position 5 and a 30A in position 8 according to my manual; both associated with "Radiator fan".

[Ben Cordy]

Yeah checked both and they are intact! So much for a simple fix!

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[Breezy_Pete]

If you have the fan control module replaced, I'll give you a fiver for the old one. I'm curious to know what's in there and what's failed.

Maybe worth considering a scrapyard/ebay replacement if your garage quote big money?  Can you see a part number on it?

[Ben Cordy]

If you have the fan control module replaced, I'll give you a fiver for the old one. I'm curious to know what's in there and what's failed.

Maybe worth considering a scrapyard/ebay replacement if your garage quote big money? Can you see a part number on it?

Ha I'll let you know if it goes that way! I'm not sure of the part number but almost everywhere I look seems to suggest it's the same control unit in all the fabia, polo and mk3 golf range. Should mean there's an easy to find replacement out there!

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