how have people done this? i thought a fan had to be wired to come on automatically, its got to be the best way.

but i think i've noticed a lot of people just wiring them into a switch on the dash?

is this quite acceptable?

i gues its better that it comes on and off on its own when it needs to , but a simple switch on the dash would be a lot easier. i guess you only need to switch it on when stationary?

How many amps does your fan draw ?

Mine is about 7A after the initial spike.

So mine is Fuse to Fan to Thermo switch to Earth.

Works just fine.

Some people add a switch so they can have a back up if the sender goes down or if they want to put it on early when in heavy trafic.

You can have it both ways. Put a permanent live feed to it and earth it via a thermostat in the cooling system or via a relay / dash switch (using a switched live to the low voltage side of the relay containing your dash switch)

can i use the same sender as my water temp gauge sender? for some reason i can't get my head round how this one works.
a switch on the dash would do me for starters i think, once you're moving it should keep cool enough anyway.

on my bmw it has one of those viscous coupling fans, i think its shot. the car heats up and starts to over heat in traffic, but once moving its fine.
so in traffic i open all the windows and put the heater fans on full. does the job nicely. i don't imagine its much different to that.

just wondered if people had done that or not, and if it was allowed

Nooooooooooooo!

The temperatuer sender is a variable resistor not a switch.
You'll burn out the sender (and possibly the dial) if you try and run the fan through it. You need a fan switch.

Most radiators have a switch screwed into them. Otherwise you can get kits from people like Frost which go into a radiator hose.

As Ben b says the gauge switch is a different type.
Youl need a switch in the rad or something rather than just relying on you turning a switch on only. If your having fun youl forget to turn it on and cook it.

as ben said, temp sender is effectively a variable resistor - you could use the signal but it would require additional; electronics.

on production cars, the fan is switched by a switch plumbed into the radiator; there are aftermarket kits that allow the tempearature at wchihc the fan comes on to be varied e.g. Kenlowe.

you can wire the fan to be switched by radiator switch, have manual override to trun it on and even off. the last case you would do if it were an off-roader prior to wading.

(I have diagram on photobucket to sow how this is done but too slow for me to access)

I had a friend who just wired it to the ignition so it's running when the engine is. Never known of him have one overheat!

When having the fan on with the ignition does it have any positives or negitives? no pun intended

Well for a positive you'll never overheat cos the fan's running all the time. The only negatives I can think of is you might burn the motor out and for that few seconds before you start the engine the fan's running so it sounds like you're running it really hot

fan running when engine is running is not the bees knees ^^^ has us believing as any coolant flow is due to siphonic action.

The place that is hottest - cylinder head - may still overheat.

Also if there is a fault or battery charge is low, then the battery could be drained.

Having said that, pretty sure my volvo is wired to do this as well as my kit car; neither have given me any problems. With the latter, I remove the battery isolater when leaving the car so the fan then truns off.

oh, and here is ther cricuit as mentioned.
Rescued attachment DSC01052.JPG

Well I didn't know that, it's just I never heard him complain about it overheating. I suppose if it was the best way then why don't bmw do it?