Radiator fan issues

[MackyM]

The fan only works erratically. I have tested  bridging the connectors with a paper clip and it fires up immediately. I have replaced the switch with a band new one and it's made no difference. What else could possibly stop the fan kicking in? Recently the lecky windows have become erratic too - is itpossible I have a bad battery and fluctuating power or is this nonsense? Thanks fellas.

[Uruk Hai]

I would have a good look at your fuses and relays if a few things are playing up

[Veedubgt18v]

also your earths.

[MackyM]

Thanks for the replies. I have checked all the fuses, and the relays seem ok. The earthing from the battery seems fine - the only piece missing is that little one at the rear, nearside corrner of the bonnet which has been absent for ages.

The only thing I can see are exposed wires going into an engine sensor. It is the small blue one at the top, front, nearside corner of the block - with a black wire and light/dark wire connected to it. Could this have any bearing?

Connected question: How hot would you expected the coolant to get before you can hear it boiling in the system (wth engine just turned off)? Logically I guess it would be 100C (being basically water, etc.) but on my car it seems to be audible only when the indicated (oil) temperature is at around 110/112. I'm wondering if my dash gauge is overreading.

[rubjonny]

it should be much higher than 100 degrees, as its under pressure.  With the correct mix of antifreeze the boiling point should be even higher!
I'd say about 150 degrees before you start to worry.  Remember oil temp isnt a real indicator of how hot your coolant is

If you can hear your coolant boiling then it isnt pressurising properly, replace the header tank cap with a new blue one, then check for leaks especially at the 2 plastic flanges attached to the head and the radiator.

[MackyM]

OK, thanks mate. And the sensor/wires??

[rubjonny]

can you let me know exactly what colour wires are going to it?

[MackyM]

Wires are black and green/white.

I disconnected it this morning and, although it's early to say, the fan seems to come on now.
I've remembered that back in the very cold weather the car would die if the throttle was pressed for the first few minutes after starting. When this sensor was disconnected the problem went away. I reconnected it a couple of weeks ago to see if the hot weather made a difference - the car seemed to run ok but then the fan problem started. What is this sensor and how can it be responsible for all this??

[rubjonny]

Ok looking at the haynes, it could be the thermo switch for choke or the cold start valve.  This seems to tie in with the fact that when its plugged in in the winter it gives you running problems?

[MackyM]

Cold start valve rings a bell. That couldn't really have any bearing on my fan not kicking in then, surely?