Intermittent failure of electric cooling fans

1995 Jaguar XJ12 6.0 cooling fans sometimes fail to operate causing rapid engine temp increase.

Don’t you have mechanical fan? Or the XJ12 has only electric?

In any case, if the behavior is not consistent, it is likely electric component (relay) that has a bad ground or dirty contacts.

One belt driven mechanical fan and two electric auxillary fans

I would suspect the relay. They can get “sticky” with water ingress and arcing over the contacts. Basically they need more “grunt” to pull them in. It could be the relay socket, especially if arcing has been occurring around the pins. Easiest solution is to replace the relay or swap it with an equivalent (head light relay or horn relay?).

We have experienced similar auxiliary cooling fan failures in my wife’s 1990 XJ-S convertible (5.3L V12 w/ Marelli ignition) and had to pull over to the side of the road only to confirm that the fan was not operating when it clearly should have been. Then after it cooled down a bit we continued on. At least once it was a relay, which I removed replaced. Another time it was definitely the thermostat near the water pump that turns on the fan, so I removed and replaced that. However, I had some mysterious occurrences which I never did figure out why the cooling fan wasn’t on when it should have been. After I completed some recent work in the engine bay I modified some wiring so that the “Caravan” or “Trailer” advisory light on the instrument panel now illuminated whenever the auxiliary cooling fan is on. It’s reassuring to see it turn on and off while driving to pretty much confirm that the fan is working as it should.

Our 1990 XJ-S convertible is different from your 1995 XJ12 in many ways, but in both cars relays, thermostats, and wiring can fail and result in the cooling fans not coming on when they are supposed to. I believe you have what is referred to as an X300. You might try posting on that list since this is probably more of a model specific question than a V12 question.

Regards,

Paul M. Novak

1990 Series III V12 Vanden Plas

1990 XJ-S Classic Collection convertible

1987 XJ6 Vanden Plas

1984 XJ6 Vanden Plas

1969 E-Type FHC

1957 MK VIII Saloon

Ramona, CA USA

Thanks Paul, I greatly appreciate your observations and input. My `88 XJ6 had a similar problem but was remedied with switch replacement.

Clarkecars,

I think most of these models have similar systems when it comes to the auxiliary cooling fans. Failure of the fan to come on when it is supposed to can be due to problems with the fan, wiring, relays, fuses and/or thermostatic switches (possible more components) which all vary from model to model. The important thing is to watch the coolant temperature as part of your instrument scan, know what is correct, and then take action when temperatures go outside of the proper range.

Regards,

Paul M. Novak

1990 Series III V12 Vanden Plas

1990 XJ-S Classic Collection convertible

1987 XJ6 Vanden Plas

1984 XJ6 Vanden Plas

1969 E-Type FHC

1957 MK VIII Saloon

Ramona, CA USA