Yes, I think the auxiliary fan doesnt do its job.
Thank you.
Yes, thermostats. 
I will replace H.D. fan clutch and auxiliary fan.
Hosung Moon,
I don’t know anything about the XJ12C, but in our 1990 V12 Vanden Plas and 1990 XJ-S convertible (both with the 5.3L V12) there is an electric thermostat switch that senses coolant temperature and closes to turn on the auxiliary cooling fan, a relay that provides power to the auxiliary cooling fan and a fuse that provides power to the auxiliary cooling fan. Before your start charging things out why don’t you trouble shoot your problem to see if the auxiliary cooling fan, thermostat, relay, fuse or possibly the wiring are faulty? I have had relay problems before and some unknown reasons that kept the auxiliary cooling fans from coming on when they were supposed to be on. I would look at your thermostat switch, relay, fuse, wiring, and auxiliary cooling fan to see if they are causing your problems. BTW, 100C is not that hot, it’s temperatures above that where problems can occur.
Paul
Aren’t you at least going to test the electric fan before $pending on a new one?
Here is my solution for failed OEM fan:
https://forums.jag-lovers.com/t/yet-another-auxiliary-cooling-fan-upgrade/376255/7
Maximum fan diameter that can fit into existing opening is 280mm.
Hosung,
I agree, you need to make sure the power circuit is working, the switch in the water pump housing or like the Series III the otter switch grounds the circuit that trips the fan relay to send power to the fan. you can pull the relay and jump the power and make sure your system works. the aux fan is an 11" fan, I took the shroud off the 11" HO Spal I used and modified the support, with is different from yours. JAMES LOVE used a 10" Spal and just fixed the whole fan in the opening after trimming the shroud. JOHN-JOHN used the Audi fan with the same support on your car. Either way I would consider running the fans off a new heavy duty relay and use the stock system to control the relay.
Any of these three fans would be an improvement, mine will tax your alternator if it is not a high amp output, the later XJS’s had bigger amps. Looking at the photo of mine you can see the relay mounted on the shroud. Also the heavy wire 14/16 gauge should have a high amp fuse, I use a 100amp fuse.
This is mine ready to go in, the red wire wrapped round the shroud to keep it out of the way while installing.
Dan
Thank you for your answer. It helps a lot.
I’m thinking of replacing with 11" spal 30102040.
Like you said, my car is not a high amp output, so an electrical part is a concern for me.
If I use an Audi fan, wouldn’t there be any electrical problems?
Thank you so much.
I think what you did is the best solution without damaging the car.
After replacing it with an Audi fan, it’s more powerful than original OEM, right?
But It looks like there will be less wind than Spal.
If there is no electrical problem and there is enough wind, I’d like to replace the fan in your way.
I have tried many things that i can do for more than three months with my electronic aux fan. With this fan, it is certain that the wind is not enough.
The fan did not work at all when the coolant temperature went up. So I put the thermostat aside to control the temperature that drives the fan. So now the fan operates according to the temperature I set.
But I’m thinking of replacing it because I think the aux fan will have to move more at idle.
Hosung,
OK you need a “puller” fan the 2040 is a pusher! you would use the3010 2054 the 18amp puller, also the three armed mount is different for your car, to use the Spal you will need the 6.0L fan mount (see picture) the Audi fan is a puller and JOHN-JOHN also used the 6.0L mount for it. I think either fan will be an improvement over the stock fan. If you use the Spal you will have to remove the plastic shroud to mount it on the three armed mount, also make sure the blades clear the shroud because the electric motor will break them if not shimmed for clearance.
Also here is the circuit breaker I used.
you can open and close it when working on the radiator.
Dan
