Thermo (radiator) fan stays running

My thermo fan continues to run when i switch the car off on my 89 daimler. It can run for 30 - 45 minutes.
When i unplug the yellow relay obviously it stops . I tried another relay but it hasnt made any difference.

Is there a sensor which goes faulty and where can i get a new one?
My temperature guage works fine .



How have you wired the thermal fan?

In the simple pre-'93 set up as originally on your '89 auxiliary cooling fan (i.e the one that only came on when the coolant temperature exceeded that which the mechanical fan managed to control), Ignition-switched power passed through the thermal switch to energise a relay which then put battery power on to the fan to run it. It was a little more complicated than that though since that switched battery power from the relay, through a diode, also was fed back to the thermal switch so, as long as that switch was ‘made’ (coolant temperature above 90 degrees C) the fan would keep running even after the ignition was switched off until the thermal switch opened (coolant temperature dropped below 90 degrees C).
The '93 /'94 twin electric radiator fan set up is far more complicated and you would need to study the circuit diagrams in CD-Rom JHM1130 to replicate that system.

NOTE that the coolant fan thermal switch is mounted in the bottom of the radiator and has nothing to do with the cabin coolant temperature gauge which is independently driven from a sensor in the top of the thermostat housing on the engine.

Are you working with a copy of the circuit diagrams?

thanks for the reply. I havent touched the wiring at all so it should be wired as standard. I think the switch may be faulty as my coolant couldnt be above 90 degrees for so long.

Could you confirm what the switch looks like? Is it a light blue round plug with 2 white wires coming out of it?

I dont have the diagrams, although i have the haynes manual on order!


Yes, the thermal switch connector is blue with a White/blue wire and a White wire to it - item 13 in this picture

I’m still puzzled about what you have actually done if you “haven’t touched the wiring at all so it should be wired as standard” Why were you then looking for ignition switched power in the engine bay?

So you have removed the mechanical fan off the front of the water pump but retained the pump itself? But have you also removed the electric auxiliary fan from in front of the radiator? That is the one which is connected to the thermal switch and operates at coolant temperatures above 90 degrees C. Below that temperature, the mechanical fan does the necessary cooling. How have you arranged for your ‘thermal fan’ to do that job from engine start?

BTW, Haynes is pretty useless as a guide to the electrics on these cars. The only useful circuit diagrams I have found are in the JDHT CD-Rom JHM1130. You should kill for a copy of that if you want to work on the electrics on these cars.

I think your getting confused, i havent done any modifications to the car. I still have the engine fan which is run by the water pump. The fan which is continuing to run is the electric fan in front of the radiator.

I will try to find another thermal switch:)


Whoops! Sorry! I must be confusing you with someone else who was doing that. :slight_smile:

[Like Mark here - Ignition + under bonnet]

I’m having a similar issue on my 94 xj6 Gold, However on mine everything bar the engine running is still powered up.
I’ve changed the ignition switch, the cooling fan relay (the awkward one under the wheel arch) and the DC1009 relay box

Any tips ?
Many thanks Elliot


By that statement, do you mean that when you switch the ignition ON without starting the engine, the ignition remains ON after you have removed the key?

If so, remove fuse A5 in the left fuse box to disable the Ignition ‘ON’ relay. If that doesn’t kill the ignition then the ignition ‘ON’ relay is stuck closed. It is ‘conveniently’ located behind the radio under the dash! :frowning:

Hi mate.
With the key removed, everything works
Ignition lights and engine go off but everything else works
I can shut the heater, radio off etc but the engine cooling fans continue to run unless I remove the fuse or disconnect the battery.
I’ve changed the fusebox both sides of footwells, ignition switch too
It will even run with Db10009 removed
Thanks Elliot

AFAIK, relay module ‘H’, DBC10009, has nothing to do with the cooling fans so its removal should have no effect on them. I assume that when you remove DBC10009 the radio, blowers, power seats and windows do NOT continue to run?

All of those above mentioned items do of course normally only become ‘live’ when the ignition key is turned to the ‘accessory’ position (I) which energises the relevant relay H1 in DBC10009 by putting it to ground through the ignition switch. Therein perhaps gives us a clue to the coolant fan problem.
The coolant fan(s) on the '93/'94 models are activated through relays in the fan control relay module, being energised by either of three switches.- the ‘radiator thermal switch’, the ‘single refrigeration pressure switch’ and/or the ‘triple refrigerant pressure switch’.
The only one of those switches which when activated energises the fan control relay by putting it to ground via the ignition switch at position (I) is the ‘single refrigerant pressure switch’. That occurs normally when the refrigerant pressure in the A/C system exceeds 218 psi which I believe ensures cooling fan operation to aid the A/C cooling effort.

None of that explains why the cooling fans continue to operate when you remove the ignition key but the clue is that the continued operation of those fans AND of the radio, blowers, power seats / mirrors etc would indicate that a) the wiring to or from the ignition switch at position (I) is still at ground when the key is removed (allowing the radio etc to continue to work) and b) there is also a fault in the single refrigerant pressure switch or its wiring which is causing the coolant fan relay to remain energised to allow the fans to continue running.

There is a White/brown wire from pin 3 of the 12-way connector on the lower right of the steering column which provides the ground link for all of the above when the key is in position (I). Since you have already changed the ignition switch itself, I would look for a snag in that wire which is perhaps shorting to ground somewhere and then check that wire at the single refrigerant pressure switch (2-way black connector on high pressure line) - item 12 in this picture -

Of course the problem may be MUCH simpler than that - but I’m not doing simple this evening! :slight_smile:

There are a couple of technical service bulletins (TSB 86-140 and 86-163) that address cooling fans that continue to operate with the ignition off. They are available here: Might be relevant to the issue you are having.[quote=“elliotxj6gold, post:9, topic:351317”]
I can shut the heater, radio off etc but the engine cooling fans continue to run unless I remove the fuse or disconnect the battery.


WOW! those are good ones! I had not seen those TSBs before but I suppose they come in to the category “Who’d a thunk it?” in the Jaguar list of weird faults!
I did say it could be something simple - and they are a perfect illustration of ‘simple’ - now I am curious how those ground points/ harnesses affect the radio, blowers etc which also stay ‘live’ when Elliot removes the ignition key. :slight_smile:

Something to investigate today now.

Quite an indepth message.
I must say I thought changing the ignition switch would have sorted the issue.
I did forget to mention this issue started after some complete toe rags attempted to steal it , thus making me think ignition switch

Many thanks
I’ll take a look at it

Hi Mike
That link you sent me is spot on. Has a whole load of info on it
I may forward it to a complete arsehole who is on here
The blooming idiot was trying to tell me that my car can’t possibly do what it is doing and had me as some kind of fool
Can’t wait to try what your bulleting states and prove him wrong
Many thanks

Elliot, I hope you do find the solution to your problem. Keep us posted - that’s how we all learn and build this database of knowledge of our cars. Good luck!

I’ve had 40’s since 99 . I’m quite knowledgeable on them however this issue has me head scratching.
Also I live in Coventry. I’m the only male in my family that hasn’t worked at jaguar
My dad was an apprentice there in the 50’s, He worked on NUB 120, the gold plated Earls Court motor show car too, he was there when the plant burnt down.
My uncle was superintendant of the E type and limousine shop and Xjs devolpment
My dad left in 67 to become a policeman my uncle got the sack after 27 years for knocking a manager out
They have some great tales to listen to.
ie guys fitting complete trims blindfolded only to find out each piece of carpet, seat , door card etc was a different colour .
My dad has told me one time when a strike was pending Sir Lyons said " go on then I’ll knock the factory down"
Also watching the D types get crushed etc
Filling Sammy Davis jnr’s chassis with ball bearing so it rattled .
Think thas was the good old days

Dear Ryan,

I think you need to check the temperature sensor in your radiator if faulty. And why not to flush the radiator maybe it was dirty so the temperature sensor wont work properly and the fan cannot cool the radiator fast.

What is the location of the cooling fan relay on a MY 1989 car? :thinking:

It’s behind the right front lamp