The 'E' Type Forum

My car passed its MOT this morning. Unfortunately during the test the cooling fan failed resulting in lots of steam and coolant all over the place.

Back home I checked the dashboard fuse was OK, then connected +12V directly to the fan's wiring connector - nothing. Checked out the negative side of the fan to see if it was getting a good earth but it wasn't. So wired both sides of the fan directly to the battery and it worked fine. Therefore I guess the problem is a bad or broken earth somewhere. The fan wiring disappears into the main loom feeding the bonnet connector and the horns.

So the question is does anyone know where the chassis or ground connection is made off to from the fan motor's negative side?

Whilst I was at it I also tried to find the fan relay (a Lucas 6RA?) .
I see in another post - 'The fan relay fits on the outside of the header tank support on the drivers side (RHD)'. Well I cannot find it. Looked in the Jaguar Service Manual and on page P.X.s.27, fig 22 there is a drawing of it, but it doesn't look like a S1 4.2 to me, maybe an S2.
The Otter switch wiring goes into a main loom near the distributor and together with the fan wiring should end up at the relay wherever it is.

Any other views on locating the fan relay?

Thanks in advance for any assistance.

Steve, stop the hunt, you don't have one! Jaguar deleted the relay on the S1 4.2 cars. I fitted a halfords one to my car, hidden inside the header tank mount.

I think the fan relay was deleted on the later 3.8's as well. The fan body is not earthed. There is a postive G/B and -ve B going to the motor. Sounds to me you have a faulty Otter switch which is quite common as they are very unreliable. Basically the Otter switch closes and completes a path to negative earth for the motor.

You can test it with a OHM meter and a pan of boiling water to see if it works but an even quicker way is to switch on the ignition and connect the Otter switch centre pin lead to earth - motor should run, in which case the Otter is indeed faulty. I would suggest you fit a Cool Cat Otter switch which looks like the original but it is from a Mitsubushi (I think) so very reliable. Ken Verity sells them in the UK - you will need the mount and the sensor.

Thanks Angus.

So the well known wiring book for the S1 4.2 that I bought is wrong once again.... it shows


I see that the other well known diagram for 4.2s does show no relay

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I checked my wiring colours and it has the loom wires to the fan being BG and B, so more like the first diagram than the second. However I put an earth onto the B and the fan came on with ignition on.
Also I pulled the connectors off the Otter switch and shorted them and the fan came on.
So it looks like a failed Otter switch.
Mine is the 2 bullet connector type (C45086) which is generally listed for the S2 but presumably later S1s had them?

David

Thanks also for your response

I think all 4.2's had the spade connector type. The early 3.8's had a knurled nut and O ring. http://www.coolcatcorp.com/Merchant5/me ... ry_Code=CS

Just looked at the Coolcat option, see http://www.coolcatcorp.com/product/FS6.html

However for S1 4.2s it says you need to fit a relay.......

David

You may well be right.

Does the spade connector type earth via a lug on one of the fixing bolts?

Yes it connects to the spade. As regards the relay it is a very good idea and is probably the reason the Otter's fail so often - having to switch the high current fan motor. Simply buy a 3.8 relay and fix it to the side of the header tank mount as Jaguar did # C18122.

For anyone interested - just ordered a Coolcat switch from Ken Verity, 01709 838352 .
He sells them complete with a simple relay included for ?34 plus ?5 p&p (cheque only).

He says some 4.2s in his experience did have relays, but most don't.