My electric fan is running continuously while the ignition is on.

I disconnected the temperature switch and it still activates with the switch on. For now it's disabled by pulling the in-line fuse.

I recently did an A/C delete and from reading the diagrams is s57 it seems to me that the A/C must be the source of power for the always-on fan I have.

Can anyone suggest to me what I've done by disconnecting the A/C that I need to rectify to prevent all this unnecessary cooling? The full A/C harness is still in place, and not grounding on anything.

 

What year is your XJS?

You didn't do anything by disconnecting the A/C.

Since the system wiring is intact it doesn't 'know' that you've eliminated anything.

The system was designed so that the e-fan runs whenever the compressor clutch is engaged....and the compressor clutch is engaged in all climate control modes, even when heating is called for. This ...both the e-fan circuit and the compressor circuit...was changed circa 89 on some models.


I don't have my diagrams in front of me but, from memory.....

Go to the compressor relay. There I'll think you'll find the wire that powers-up the compressor activated leg of the e-fan circuit. I can't remember the color but you can experiment, or check your S57, or others will chime in

Cheers
DD

 

Thanks! Jessie is an 86.

Your summary is exactly what I understood to be the setup. I believe the AC to relay wire is green or light green. I'll meter back and try to figure out what's up today.

 

Thanks! Of course it was running all the time. It's supposed to. Running the AC with the heat on because it's cold out would obviously require also running the electric fan to carry away all the heat the AC is pulling out of the heated cabin. Simple physics. Don't know why I missed it.

Disconnecting the brown with green tracer wire ( GN ) from pin 3 of the diode pack defeats the AC trigger signal for the e fan. Otherwise it should behave normally, coming on with its temp switch and staying on until cool while turned off hot.

solved.

 

My fan doesn't seem to want to work at all. I'm sure that it used to. According to the '92 wiring diagram it should be on with the temp switch or the A/C. Can the diode pack be checked ?

 

That may be a benefit but the reason for running the a/c compressor in all modes is to dehumidify the air. All incoming air is first refrigerated and dehumidify and then heated as needed. This is why you never see a Jag running around with fogged-up glass

Starting in late '88/early 89 Jaguar changed things up a bit...with the e-fan not necessarily being tied to the compressor circuit and different compressor circuits for coupes versus convertibles.

Good work !

Cheers
DD

 

Sure !

I don't have the later diagrams to give any specific hints, tho.

Cheers
DD

 

First check the inline fuse. If it's good then short the temp switch connector on the front of the block. Turn ign to ON. Does the e fan run?

If it does: At least 1 of three Diodes are good. And fan is good.

If it does not: test for power to Diode on double ( 2 ) light green wired plug.

If that has Power: test single light green wire on diode for power. If it does not have power then a diode is bad. If it does then you have a problem in the wiring between the diode pack and temp switch or between the temp switch and fan or a bad fan.

 

From 89 (at least) the cooling fan did not come on with the AC.

The cooling fan relay is on LHS of the engine bay. This relay is supplied power by the thermo switch on the water pump inlet, via pin 4 of the diode pack. So with the ignition on you should have 12 volts on pin 2 (input) and 4 (output) of the diode pack.

 

Thanks guys l will test that out later toay.
On the thread about headlights is the '93 wiring diagram (fig 24 page 61) that has the same fan wiring as the '92 diagram. Looking at that then yes it is also controlled by the A/c.

http://www.jagrepair.com/images/Elec...Electrical.pdf

 

It can not be controlled by the AC the diode between pins 4 and 5 would be reverse biased and not allow current flow to the fan, this diode is there as a flyback for when the fan turns off, its purpose is to prevent spikes damaging the electronics.


Here is the 1992 electrical guide it

http://www.jagrepair.com/images/Elec...electrical.pdf

 

Ok. With the diode out l have power on 2, with the diode in power on 4 too. If l bridge 2 and 5 the fan runs.
When l jump 30 to 87 on the fan relay the fan works too. Also if l power 86 the relay clicks and the fan works.
Only thing l haven't checked is the thermo switch.

Hmmmm seems the two connectors to the thermos switch are unplugged....... jumped them and all ok'

Thanks guys

 

That'll do it.............

 

Heck, As since the wires are already unplugged you might as well go ahead and jumper them together to see if the rest of the circuit works!

Cheers
DD