Club 80-90 Forums

sternal wrote:

Jump that to the other connector, and the fan works, providing the engine's running, yes?
OK, I can live with that.

No if I did that then nothing happens

if the two wires that are connected not the +12v feed are connected this will make the fan run on other speed...

Run that by me again?

You have three connectors. Let's call them A, B, C.
A is +12v to earth.
A-B gives you fan.

Are you saying B-C, rather than A-C, gives you the other fan speed...?

How are you determining which is +12v? One probe on the bodyshell for an earth, one in the terminal?

all this without ignition on...

So there's no difference with?

Not really - it was working correctly but you have done something and now it isn't.
^^^ meant for the post before.

He had two speeds, he messed with it and now only has one. The red/blue trigger is not functioning now due to? - earth knocked off? - trigger replaced on wrong terminal? - or?

Not really - it was working correctly but you have done something and now it isn't.

was a loose wire so is working as I said

Are you saying B-C, rather than A-C, gives you the other fan speed...?

yes this is how it was yesterday


but to be double sure I am going to run another test this eve...

^^^ that is not what you put earlier!

^^^ that is not what you put earlier!

its got confusing I'm going in circles with it all...I will double check this eve as now its working as it should ie when bridging like yesterday (Sunday)

I really do appreciate all your help and I hope the usual crew aren't along to start gloating and sneering after all Im doing what this site promotes and that's having a go myself...

Will post back this eve with some details...

This pic might help with folks understanding what you are seeing;



So if you connect the "Red/White" wire to the "Black/Red" wire at the 'radiator fan thermoswitch connector' then you should get the slow-speed fan setting - and from your posts I think that you have said that this is working.

If you connect the "Red\White" wire to the "Red/Blue" wire then you should get the high-speed fan - I think that you are saying that this does not work.

So you have tried putting a relay into slot 5 - but that is still not working.

Try this;
Put a relay into the slot 5 position.
Get someone to connect the the "Red\White" wire to the "Red/Blue" while you have your ear against that relay - you should be able to hear the relay click.
Can you hear it click????

I assume you will not hear it click - in which case my best guess would be that the brown wire from that relay position is not getting to a good 'clean' ground and that is preventing the relay from operating. But it could be other things ..
Anyway before we get ahead of ourselves - report back when you have tried the above test??

So if you connect the "Red/White" wire to the "Black/Red" wire at the 'radiator fan thermoswitch connector' then you should get the slow-speed fan setting - and from your posts I think that you have said that this is working.

If you connect the "Red\White" wire to the "Red/Blue" wire then you should get the high-speed fan - I think that you are saying that this does not work.

So you have tried putting a relay into slot 5 - but that is still not working.

Try this;
Put a relay into the slot 5 position.
Get someone to connect the the "Red\White" wire to the "Red/Blue" while you have your ear against that relay - you should be able to hear the relay click.
Can you hear it click????

I assume you will not hear it click - in which case my best guess would be that the brown wire from that relay position is not getting to a good 'clean' ground and that is preventing the relay from operating. But it could be other things ..
Anyway before we get ahead of ourselves - report back when you have tried the above test??

Will try this when I get the correct RELAY NO.53 spoke with the nice guys at VW Heritage and they said needs to be that relay, at the moment I have a "standard 30amp" relay which I was told would be fine from the local car spares which now looking at Halfords there are 3 standard 40amp relays and if there are 3 standard types from Halfords then which is the correct one ??! ! so the fact I have the wrong one wont help matters.

If I do the wire test without the relay should both speeds still come on ? as I will try this this eve checking of course all my earths first. the relay I have at present may be busted for all I know !

will try the test in a few days when the relay arrives.

just incase anyone thinks why I don't have the original relay its because it was missing !


MidLifeCrisis thank you

sternal wrote:If I do the wire test without the relay should both speeds still come on ?

Low speed, yes.
High speed, no.

A relay's just an automatic switch. When the rad switch says "High speed, please", current is passed to the relay, which then closes and sends +12v to the fan. They do it via a relay so that more power can be sent than the rad switch could reliably handle.

Given that the terminal designations (30/85/86/87) are the standard relay designations then I'd have thought any relay which fits would work - and a quick google finds 53 certainly _looking_ like a normal relay. 40A, apparently, but I can't see the fan drawing anything like 30A (and it's a 30A fuse in the wiring diagram), so a 30A relay should be just fine.

But if VWH reckon it _has_ to be a specific VW relay, then <shrug>... Enough 53s on eBay for a quid or so...

MidLifeCrisis wrote:This pic might help with folks understanding what you are seeing;



So if you connect the "Red/White" wire to the "Black/Red" wire at the 'radiator fan thermoswitch connector' then you should get the slow-speed fan setting - and from your posts I think that you have said that this is working.

If you connect the "Red\White" wire to the "Red/Blue" wire then you should get the high-speed fan - I think that you are saying that this does not work.

So you have tried putting a relay into slot 5 - but that is still not working.

Try this;
Put a relay into the slot 5 position.
Get someone to connect the the "Red\White" wire to the "Red/Blue" while you have your ear against that relay - you should be able to hear the relay click.
Can you hear it click????

I assume you will not hear it click - in which case my best guess would be that the brown wire from that relay position is not getting to a good 'clean' ground and that is preventing the relay from operating. But it could be other things ..
Anyway before we get ahead of ourselves - report back when you have tried the above test??

I have been all through this already!!!!
Diagram, explanation and all.
No need to keep repeating it!

I have been all through this already!!!!
Diagram, explanation and all.
No need to keep repeating it!

lol !

I reckon the relay is fubar or one of the earths is off...

will give it another go this eve with the relay i have (took other back)

phewwwwwwwwwwwwww !

sternal wrote:I reckon the relay is fubar or one of the earths is off...

You know the fan motor earth's good, because the fan works on low. So check the earth to pin 85.

Jumper the high speed pair in the fan switch, and make sure you've got +12v to the relay's pin 86. If so, the relay _should_ click. If it doesn't, the relay's duff.

Now make sure you've got +12v to pin 30.
Then jumper 30 to 87.

You know the fan motor earth's good, because the fan works on low. So check the earth to pin 85.

I'm lost after those instructions...out of my league there I think...which is why I loose and I have to use a mechanic...


We now know both speeds work!!!!!!

I can confirm both speeds work I found a relay in the boot marked 24 (could it be the missing one it says 40amp)
I stuck it in and hey presto both worked !

30amp relay bust



Sorry for the blurryiness numbers read
30 87
85 86

So I guess knowing this rad switch needs replacing ????

Easy job ????

sternal wrote:So I guess knowing this rad switch needs replacing ????

It's the usual reason...

Easy job ????

Yep. Lower grille off, unscrew the old one, screw the new one in. A little coolant lost, but not much. The rad will need a little bit of bleeding when it's up to temp - get somebody to hold it to ~2k rpm, loosen the bleed screw until unbubbly water comes out, retighten.

Have you read anything that I posted? The rad switch will only work IF the rad gets hot enough. It doesn't work in normal use - just when it reaches the set temps. It will never switch until the temp is reached.
Just leave it alone now and worry about the switch when you manage to get the rad hot enough.
Please.