Electric fan operation

I recently suffered an embarrassing boil up in my R4 whilst queuing in traffic. Niether the electric fan or the temperature warning light seemed interested in coming on. I've subsequently tested the fan operating switch and found that it doesn't operate until 96°C (cutting out at 86°C). A spare one tested at 94°C/82°C. As the switch is mounted near the outlet of the radiator these figures seem very high - can anyone advise whether this is the correct spec?

Also, if the switches are as they should be is my problem that the cooling system isn't holding pressure and allowing the coolant to boil at 100°C rather than something higher?

Guess I'll just have to sit in traffic with the heater fan on full blast in the meantime...

Go back to basics first. Take the wire off the sensor attached to the cylinder head. Turn the ignition on and earth that wire - ask a friend to tell you whether the warning light comes on or not. If not, then try a new bulb or see if there's a dirty connection on the printed circuit. Once you've established that the light works, re-connect the wire. Next thing to check is the thermostat in the top hose. Start the engine from cold and turn the heater valve on. As the engine warms up, hold both heater hoses and make sure that they get hot. Soon after, hold the top hose to check that hot water is going through. If not, replace the thermostat. Do not be tempted to run the car without it. Bleed the cooling system to expel all air bubbles keeping the resevoir bottle held high above engine level. Top the system up through the bottle at all times but keep the level around the max mark.
Once all air has been expelled, fit the bottle in it's holder and run the engine, still keeping the heater valve on (but not the fan). You should see the fan come on, but if the engine shows signs of boiling via the warning light and the fan does not come on, fit a new sensor and check again.
I am assuming that you suffer no water loss through a leaky head gasket as this would cause the symptoms you describe.

Good luck and let us know how you get on.

Steve

I've just re-read my post. When I said replace the sensor, I mean the one in the radiator that operates the fan.

Steve

Those electric fan thermostat temperatures seem a little high, but the fact they are so consistant makes you think they can't both be wrong.

My guess is that the coolant will boil at around 105 degrees C. The thermostat is in the outlet of the radiator, and you would expect around 10 degrees C cooling across the radiator, so you wouldn't want the outlet to go over 95 degrees C at the very worst. I'd have said a 90+ degrees fan switch was cutting it a bit fine. I have a battered old switch lying around in the garage that you can test. If that gives the same result then surely they can't all be wrong.

Definately worth doing the other things Steve suggested first, then running the car up to temperature to see if the fan comes on before steam starts coming out.

:lol:

Steve, Mr/Ms C. Cat,

Thanks for your coments. I have at last go round to trying a few things:

The temperature warning light sender looked a bit sick when inspected and so I think this is the reason the warning light failed to operate. I haven't checked to see what temperature the replacement comes on at though. The light works when the sender wire is earthed.

The fan operating switches (a sample of 4!) I have tried all switch on only at surprisingly high temperatures (94-100°C) and so my first one must have been "normal". I can only think that dirty contacts prevented the fan from cutting in when the car boiled over. I don't think I have head gasket trouble (yet!) as I've packed in a fair few miles since without significant coolant loss. There also seems to be no problem with the thermostat.

The best thing from here seems to be to carry on regardless from here...

thermal fan connection R4 F6

Hi- I have recently purchased a 1984 F6 here in France- I have recently replaced the clutch and found upon remounting the radiator that the electric fan is not connected, nor do there appear to be any wires I can connect it to- would someone please tell me where it connects to? I can see the thermostatic switch and wiring in the radiator, but they go into the main loom.
Thanks for any help.
Ian