XJS 1993 Electric cooling fan

[baz234]

Does anybody know at what temperature the electric cooling fan switches on? The viscous fan is OK and I can spin the electric fan blades, but I have noticed the temperature moving quite close to the 'hot' section on the dial, especially in stationary traffic. Logically it could be a sensor, but I have no idea where that is situated.

[mwsmith29]

Hi Baz,
I came on here looking for the same answer. Anyway I have now consulted Volume 2 of the XJS Service Manual. This is what it says;
"The fan is thermostatically controlled and in very hot conditions it can operate after the engine is switched off. The fan will automatically switch off when the coolant temperature drops below 90 deg C".
Note that the thermostatic switch that controls the auxillary fan is screwed into the top LH side of the radiator. To access it you need to remove the air filter housing on 4.0 litre cars. On v12 engined cars the thermostatic switch is fitted to the front of the water pump elbo but it should be reasonably accessible after removing the header tank.
To test the circuit including the relays is easy. Seperate the plug connector from the thermostatic switch and use a loop wire to short out the terminals on the harness side connector. Switch on the ignition and the fan should run, when you switch off the ignition the fan should continue until you remove the loop connector.
If the above test is successful then I suggest removing the Thermostatic switch and connect a multimeter set to OHMS. Suspend the switch in a pan of water with a thermometer. Neither of which should touch the bottom of the pan. When the water temperature is above 90 deg the multimeter should change to a low resistance reading.