I want to fit a small bilge blower to my engine bay to cool the car down when parked up after a drive. I think having it set to about 50°C would be an ideal temp for it to cut in (or cut out below).

Has anyone got any ideas how to make/buy a switch/thermostat to achieve this? Forgot to mention it is 3A 12v
Rescued attachment bilge blower.jpg

http://www.maplin.co.uk/Module.aspx?ModuleNo=220003&doy=8m9&C=SO&U=strat15

too easy
£6 from Maplins...

Have you got a thermostatic switch on your rad fan? If you do then wire you fan to permament live - even without the water pump running you get a convective flow which is really good a quickly cooling the engine.

Mine will run for 2-3 mins after a serious threp and it gets the whole engine cooled down nicely.

I must admit that that was my first thought!
Why bother with the bilge pump when there's a perfectly good temperatre switch and fan at the front of the car? and adding the bilge pump + switch will add to the weight of the car.....

The maplins PCB looks good - unfortunately they are out of stock

My rad fan only cuts in when VERY hot and will only run after the ignition switched off for a few seconds.

I had thought of fitting a rad fan switch very close to the exhaust manifold, but do they only work with water?

I get a lot of rude remarks about my rad fan - it goes on for 5 or 10 minutes after shut-down!

Strangely, it sometimes takes 1 minute before it starts... probably the water gets heated up by some hot-spot, then circulates round to the fan...

http://www.circuit-innovations.co.uk/thermsw.html

http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=31698&doy=8m9

but the max switch temp is 30degC.
Changing the NTC thermistor or the adjusting potentiometer might make the range greater.

Actually, I've just had a look at the manual for that module. You could adjust the range many ways. Simplest would just to put a resistor in series with the thermistor. That would move the switching temperature into a high temperature for the same threshold resistances....

Would it be safe to run a 3A motor with a 3A controller?

quote:

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Originally posted by Mark Allanson
Would it be safe to run a 3A motor with a 3A controller?

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I just found an old Nissan Micra rad switch and tapped in into my exhaust heat shield - It works!!

Mine does exactly the same!
A great piece of engineering!

quote:

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Originally posted by David Jenkins
I get a lot of rude remarks about my rad fan - it goes on for 5 or 10 minutes after shut-down!

Strangely, it sometimes takes 1 minute before it starts... probably the water gets heated up by some hot-spot, then circulates round to the fan...

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Why not change the fan switch for one with a more suitable setting? Check out your local motor factors, the operating temperatures are engraved on the brass body. Also found some vents in the bonnet helped greatly. Like David my fan runs for ages after stopping and drops the under bonnet temperature a treat