When does the small electric radiator fan come on and why is it there? I have never seen or hear it come on.
Thank you.

 

It should kick when the coolant temp reaches 201ºF or thereabouts.

Try jumping the terminals at the temp switch located in the water pump housing and see if the fan comes on. If it does the circuit is Ok and either A) your coolant isn't hitting 201ºF or B) your coolant IS hitting 201ºF but the switch is faulty

Cheers
DD

 

The relay could be at fault too.
Also, some fans were wired to come on when the air conditioning was switched on and some weren't.
Mine has packed up again so I am going to fit a live feed and switch to it and operate it manually.
Does anybody know where I can pick up a live feed from in the engine bay? (on the Cabbie).

 

There were variations year-to-year and engine-to-engine. On the XJS in question the e-fan was temperature only



On Jags of that vintage any solid brown wire is constant 12v battery voltage. If that's what you want (as opposed to switched voltage) then go to the existing cooling fan relay socket. There's a solid brown wire right there :-)

If you run a manual switch make sure to get one that will handle the current of the e-fan. Ideally, you'd run a relay even with a manual switch, though.

When you say "Mine has packed up again...." it sounds as though the relay has already been replaced recently. If that's the case I'd make sure there isn't a problem in the circuit as these relays usually last for many years. Perhaps the motor is drawing too much current? Or poor connections at the relay socket? (Look for charring)

Cheers
DD

 

Thanks Doug.
I haven't had a chance to check whether it is a relay fault again (there wasn't one there at all when I bought the car) or something further up the line. I didn't notice any charring when I fitted the relay but who knows.
The radiator is being replaced soon so I'll have a bit more space to ferret around in with my big, fat hands once it is out.