Guide to fitting a fan override switch for track use.

mty12345

Active Member
Jun 17, 2011
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bristol
I thought i'd make a quick guide on fitting a manual override to the cooling fans, so that you can switch on the high-speed fans for extra cooling after a few laps of the track. It's not going to be a full step by step guide as i'm not actually fitting it to my car, but more of a rough outline as to how to do it.

I should make it clear that the fans were NOT designed to run at high speed for any extended length of time, so they shouldn't be left running in this mode for more than a few mins to help cool the car down. They're pretty loud at full speed so i'd say it's unlikely you could forget them, but using an illumimated switch or a timer would be an option if you wanted to go that far.

It's all fairly basic stuff but you will need to be confident splicing into wires and probably doing some basic soldering depending on what type of switch you use.. There are plenty of videos on YouTube about how to solder, join and splice wires, and there are also many types of splice connectors on ebay and similar places that make the job easier.

The basic idea is the splice into the wiring coming from the fan thermoswitch that is screwed into the passenger side of the radiator about half way down.

20210724_160750.jpg


It's a simple 3 pin connector that has three wires coming from it. They are:

Red = common wire
Red/White= low speed
Red/Yellow= high speed

20210724_160712.jpg


You can leave the wiring connected as it is, so that normal running isn't affected, and just splice a relay into the RED wire and the RED/YELLOW wire. Then when the dash switch is in the on position, the relay will be energised and it will connect those 2 wires together switching on the high speed fans.

You can get a 12V 40A automotive relay from ebay or amazon. Some come with a socket and wires attached which may make wiring easier. This type of relay will be overkill for what we are switching, but i'm not sure of the exact current on that wire, so it's better to go too big than too small.


What ever automotive relay you get should have the same pin numbers, even if they are in a slighty different layout. You need to connect them as below.

relay connection.png



You can use any type of switch you want for the dash, just connect one side to a switched 12v supply, (for instance for the radio) and the other side to the 'dash switch' connection on the relay as shown above.

You will need to either put the relay in an enclosure, or you could seal it with hot glue, silicone, or something similar, and then just cable tie it to the loom near where the exsisting fan control module is located.

Hopefully this is some help for anyone wanting to do this sort of mod and if anyone has any questions or can think of anything i've missed then let me know.
 
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