Wiring for electric fan switch?

[GrahamR]

My car has the standard viscous cooling fan removed and an electric fan is fitted in front of the radiatior. It is fed from the 'spare' (overdrive) fuse and is wired to run permanerntly.

Rather than fit a thermostat etc I intend simply wiring a switch back to the dash so I can turn the fan off or on manually. I'll possibly wire it to the heated rear window switch. My question is which rating of cable should I use? The fuse is rated '5 Amp Continuous, 10 Amp Blow' although I'm not sure if this is the correctly rated fuse for the fan?

Any advice apreciated.

Graham

[Peter Hills]

Hi Graham,

The fan will run best if it has the highest possible voltage on its terminals. The heated rear window switch is not completely suitable for this application. It is not intended to supply the sort of power needed for the fan. However, there is a simple way out of this problem and it's one I use myself.

I would use a common (4-terminal) relay rated at 30A and take a thick wire directly from the battery, via a fuse, to the power side of the relay, (terminal 87) then from terminasl 30 onto the live side of the fan. Earth the fan with a new wire to a good earth. This cable should be a good thick one. Typically a 27amp cable for both the supply and earth connection. A 30A fuse will be needed in this line. Ideally use a brown wire for this application.

To control the relay, take a light wire from the HRW switch to the control side of the relay (terminal 85) and another one from terminal 86 to earth. These last two wires do not need to be very big - 5A cable will be fine.

Hope this helps; if you need more advice please contact me directly; my details are in the front of the SOC Magazine.

Regards

Peter Hills
Modified Stag Co-ord
SOC

[richardthestag]

WHS ^^^

also I have used these guys

http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php

when sourcing bits, cable etc

[Peter Hills]

I've used them, too. Excellent.

Peter

[GrahamR]

Peter & Richard,

Thanks very much for the advice. I'll get the parts and materials organised and give it a go.

Regards

Graham

[KOY 23]

Graham.
I really would advise fitting a thermo-switch, especially as you don't have an engine driven fan, you will have to watch the gauge all the time. Too easy to cook the engine IMHO.

John.

[Peter Hills]

Graham.
I really would advise fitting a thermo-switch, especially as you don't have an engine driven fan, you will have to watch the gauge all the time. Too easy to cook the engine IMHO.

John.

Graham,

I would also recommend a thermo-switch. It would be very easy to fit into the circuit I described above. Please contact me if you need any more informatuin.

Regards

Peter

[GrahamR]

Had a day off work today and got the fan rewired to the HRW switch including a relay and inline fuse. Thanks again for the advice Peter. One query, I got the relay from Maplin. They did not have a 30 amp one, so I've actually fitted a 40 amp unit. Will this be okay?

Graham

[V Mad]

Dont worry, a 40 amp relay will be better than a 30 amp one.

[Peter Hills]

Graham,

Well done. Basic electrics aren't magic. Who knows what electric adventures lie ahead! Most can readily be solved, as you've found out!

Peter