2 hours ago, Wino said:

Switch on ignition, then short the brown wire pin to each of the others in turn. One should bring the main fan on at low speed, the other at full speed.  Access isn't peachy though, and keep fingers/hands clear of the blades!

 

To avoid having my hands anywhere near the fans when they come on, could I short it with the ignition off, then turn the ignition on to test?  Or would I also need to remove the blade fuse and/or disconnect the strip fuse?

13 minutes ago, jonmad said:

 

To avoid having my hands anywhere near the fans when they come on, could I short it with the ignition off, then turn the ignition on to test?

Yep, can do; it's only the high speed relay/action that needs the ignition to be on. Internals of the fan control module, J293, (on bracket on chassis leg) are like this:

 

 

 

Inputs K1and K2 are the ones that allow the A/C control module to invoke fan action when refrigerant pressure exceeds 9 and 16(?) bar respectively (from memory). MOT1 and 2 are the two rad thermoswitches

Edited 16 March, 20206 yr by Wino

Wow, amazing detail, thanks.  If the low speed fan(s) would kick in even with the ignition off (so they can carry on cooling the car after switching off after a run, right?) that means for low speed test I could take blade fuse 8 out first, then short the connector, then when putting the fuses back it that should run it at low speed?

Yep  

Expect the sparks at the fuseholder instead of the thermoswitch loom connector.

Thanks for the warning   Not sure when I'll get a chance to test anything but will let you know.

Link brown wire pin to brown/blue wire pin for low speed. 

Hello again.  Well, after some time and a lot of swearing and trying different tools on rounded off bolts, I managed to get the sump guard off my rally car.  A Dremel eventually did the trick on the last particularly stubborn bolt.

 

So anyway, I can now try and locate the thermoswitch, so as to try and short out a couple of wires to see if the fan comes on.  It's all a bit mucky under there.  Is any of of these obviously the thermoswitch?!  All taken from various orientations, looking upwards.  

 

Thanks,

Jon

 

edit: I think the first one might be the fan control module.

 

Edited 9 May, 20206 yr by jonmad
more details.

Last picture is it. Triangular plug is the giveaway.

Superb, thanks.  I'll take another look in daylight.

As per an edit to an earlier post of mine, there won't be any sparks when you link connections, and you don't need a thick wire.   On A/C-equipped cars the thermoswitch  wires only power relay coils, not the fan itself.  Be careful with the connector latch, which seems to be facing upwards, out of view in your pic, you don't want to break it off.

Thanks for the details, Wino.

I'm struggling to see how I can reach this.  I can barely get my fingertips to it, let alone get any grip on it to turn, press or pull it in any direction.  I think as the fan is running on high speed I might have to leave it.

 

Here is a pic from above.  What part do you even press to get it undone - push that tab in that's facing upwards then pull off?

 

 

Aside:  this is the bar bolted on beneath the engine and gearbox that my sump guard was attached to.  I assume this is non-standard?!

Yep, that bar is non-standard. At first glance it looked like it was bolted through the exhaust!

 

The thermoswitch connector is awkward, but a standard VW group latch mechanism. Access may be easier from below, possibly with those big rectangular fan connectors moved out of their mounting brackets.

The technique with the latches is to push the connector on initially, while gently lifting that latch (towards the cables), listen for a click as the latch releases, then pull the whole connector straight off. 

There must be a few youtube videos demonstrating this. The reason for the initial 'push' is the rubber ingress seal inside puts the latch in a state of compression, so it won't unlatch easily (and can break pretty easily if force is used). Push the connection on, and the rubber seal is compressed more, relieving the friction on the latch.

Thanks Wino for that technique.  I see what you mean about the bar - yes, that's just one of the replacement bolts for the guard, which is about 8mm thick.  It's a heavy lump of metal for sure.

 

Fab, thank you.  Now I can see how many are like that in there as well.