Thank you in advance.
I have a 1990 XJS and i have some questions about the aux fan.

1.) is it connected to the AC system? When i turn my ac on should my aux fan come on? It is a 1990, i have been told they changed this at some point-ie 1989?
2.) at what temperature will it come on automatically?

it looks like it takes a temperature reading off of coolant in the water pump?

Is there a wiring diagram someone can share for the 1990?

i checked the fuse, and sanded the contacts on the relay, and it DID come on when i turned the ac on (the car was cold and hadnt been run yet). I replaced all relays today as well to be sure (as they are cheap) and ensured all connections were solid (well visually), however this was short lived as it wont engage now as previous. Sounds like an intermittent connection. Just strange that as soon as i sanded the relay-boom it worked. Then it decided it wouldnt. Ha.
I shorted the connection down by the water pump where it gets a reading and the fan did not come on, which it should have no?

How can i tell if i have a bad switch? Anybody have a manual switch and just turn their aux fan on manually?

fan will run when given power. Is there a relay somewhere im not checking or am i missing a whole part to this system?

ANY help appreciated, as my car is running too hot in idle traffic until i fix this.

I am not especially electrically inclined so forgive me if i am not making perfect sense.

Thanks again.
Jamie
Kingston, Ontario

 

There have been two versions, and I believe a TSB ( not sure) on this. Originally, the electric fan is triggered by the thermal switch on the waterpump. It should close at 85C, and that in turn closes the fan relay and the fan should run. Note that is waterpump inlet water temp, so that is after the coolant has passed through the radiator and is coming back into the engine.

The TSB ( apparently, I have not seen it) made a modification that triggered the relay when the AC compressor clutch was engaged, in addition to the thermal switch.

You can find the wiring diagrams here: JagRepair.com - Jaguar Repair Information Resource

The thermal switch should close above 85C, and be open circuit below that. Shorting the wires at the switch should cause the fan to run. Have you tried a new relay? They don't last forever. Any generic auto relay will do, as long as the pin numbers are the same and in the same positions.

Have you gone through all the usual suspects for the cooling system? Fan clutch is good? Correct thermostats that block off the bypass - see discussion this week about those. Your radiator is clean and all the debris cleaned from inbetween it and the condenser? I have seen plenty of cars where this was never done and the radiator was half blocked with leaves, fluff and general debris that gets sucked in there.

See the photos here for the amount of debris that can accumulate: https://www.jaguarforums.com/forum/x...g-warm-206092/

 

Hi Jvickers

Its not unknown for these AUX Fans to get 'Stuck' and it doesn't take much (ask me how I know or rather don't!)

Just make sure that the Aux Fan is able to Spin Freely on its Axis and maybe give it a Squirt of WD

 

Assuming it is a V12?
if so, engine running the fan should come on if the temp at the water pump thermostatic switch is 85C or over.
It may (OEM, some did some did not, Jaguar changed their minds from time to time) also come on every time the compressor kicks in.
The switch is very unlikely to fail, so how hot is "too hot" in traffic on your cabin gauge?
If by closing the two wires to the switch the fan comes on, then the fan circuit is fine. Your only problem, if there is a problem, is the switch and the temp it is cutting in at.
To test if it comes on with the a/c compressor (not the same as the a/c being switched on from the cabin, as the compressor kicks in and out) run the car up to temp (the a/c will not start until the coolant is above a certain temp); then switch the a/c on and set cabin temp to full cold; then open the bonnet and watch what happens as the compressor kicks in from time to time.
If it does not come on with the compressor, Report back. It is quite easy to adapt the fan wiring so the fan comes on with the compressor by the way.

 

Thank you Greg. We tripped the wire at the switch and no sign of life. Just put in all new relays. Fuses all good. Must be one tiny wire somewhere on the bottom of the fan relay. The hunt continues. Simple
circuit but it is defeating me.

Any step by step you may have available regarding wiring the fan directly into the compressor would be great, thank you. The temp creeps right over N a full needle or more when it goes through “city driving” for more than about 10 mins. And its only 23celsius out at its peak maybe. I just did a coolant change and the coolant pours out of the bleed nipple when both caps
removed, so i think im properly bled. New steering rack and a waterpump installed by a local jag shop, i would hope they would tell me i need a rad job when they pulled it, but they did not. At the very least it should be clean and clear. Clutch fan looks fine no cracks, it is the original yellow.

In terms of temps, its giving me about 95-100c readings on block and 88c readings on rear coolanf hoses, this is when i just drive it 65-75mph for an hour or so. These temps seem good to me. Its the idle conditions that bother me.

Thanks again.
Jamie

 

An external visual inspection will almost always reveal the clog of leaves and debris on the forward face of the radiator, as mentioned earlier. And a visual inspection will reveal a leak. But the inside of the radiator....well, that's a different matter. it's quite common to have internal clogs. IMO, removing the radiator for professional cleaning and pressure testing is a 'must do' on these old V12s. The cooling system on these cars must be 100%.No ifs, ands, or buts about it.


Drive the car in city traffic and let the temp creep up as you've described. Turn off the engine. Now spin the fan by hand. If the clutch is good, the fan will spin only about a half or two-thirds revolution. Anything more is 'suspect' and the clutch should be replaced, especially if fighting an 'in traffic' coolant temp situation; freewheeling is bad for sure and the clutch needs to be replaced.

Cheers
DD

 

Jamie, some questions:

• have you tested the fan will run when 12 volts is applied to its lead?
• if your car is like mine (1986) the fan relay is one of three in a vertical position behind the LHS headlight nacelle, in front of the wing header tank, under a plastic cover. Yours may be there or wing mounted and obvious. Have you checked that there are 12 volts to the relay high-current input-side engine running? Have you checked that if you apply 12 volts to the trigger terminal on the relay the fan will run? Also that if you apply 12 volts to the high current output side of the relay the fan will run?
• There is a fuse on the LHS wing that controls the fan, have you checked that it is passing current, and that there is current to one side of the fuseholder, engine running? Also there is a line-fuse on the circuit to the fan, usually in a loom bundle on the LHS of the radiator top panel. Have you checked this is OK and the fuseholder passes current?
• If all of the above checks out OK, then re-check if the fan will run if you join the two temp switch wires.

Report back on all the above for more ideas depending upon the results! We will get to the always on with the aircon once the circuit is working properly. Incidentally, once the circuit is working, installing a more modern fan is a good plan too. The OEM fan is not that efficient.