I have a new (to me) 3.6 XJ-S and the radiator fans have just started to come on before I even start the cold engine. Can anyone help?

thanks

Van

Nottingham UK

 

Off the top of my head, since you said "fans" it sounds like a previous owner has converted your car to dual electric fans.

 

I'm not sure how the 3.6 cars versus V12 cars varied with respect to e-fan circuits.

On the pre-89 or so V12s the e-fan circuit was powered up whenever the a/c compressor circuit was powered up...which, in essence, was whenever the climate control switch was set to anything except 'off'. Therefore, the e-fan would come on whenever the key was 'on' regardless of coolant temp.

The 3.6 cars may have the same arrangement

Cheers
DD

 

As MacA mentioned, have you got a modified setup? The standard setup is one electric fan and one engine driven one. Under the standard setup, as Doug mentioned, there are two possible OEM installed permutations to trigger the electric fan which Jaguar used from time to time (on the V12 car admittedly; but the 3.6 has the same aircon unit so almost certainly the same):

1) triggered by water temp only, in which case the electric fan should not run with a cold engine at startup. Not affected by the aircon unit at all, and
2) triggered as in (1) above AND by the activation of the aircon compressor. That is, if the aircon/heater is switched on at all, the fan will run if the actual compressor is activated by the system. So if the system is on and the engine is cold, the fan will only run if the system is calling for the compressor to run as well - which it should not do on a cold engine on a cold day until the engine water temp has raised enough to feed hot water to the heater part of the aircon/heater unit.

If your setup is different, maybe the previous owner changed it to what you have now? Also, you can test if the fan is wired to the 'aircon on' switch rather than 'aircon and AND compressor on' by switching the Rh aircon knob to off and then turning on the ignition. Whether the fan runs then or not will tell you something.
Greg

 

To clarify-I shouldn't have said "fans". It is the small single fan at the front of the radiator on the right hand side (when sitting in the car). This comes on as soon as the ignition is turned on even when the engine is stone cold. the heater and a/c controls are all off.

Van

 

I suspect someone has modified the circuit .

Cheers
DD

 

Isnt the right hand one engine driven, left hand one is electric from drivers seat. Or the 3.6 must be different. He says in front of the radiator not as expected behind.

 

On a right hand drive 3.6 the electric fan is on the right, in front of the radiator. The problem was that the fan control relay needed replacing. All is good now.

 

Apologies van883,

I was going to post that you should check the relay and/or the temperature switch, but got distracted.

Glad you got it sorted.

 

My bad....learnt something new..