Ford Mustang Forum - View Single Post - Electrical whizzes - help please
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post #6 of (permalink) Old 10-06-2013
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Originally Posted by LandToSea View Post
LOL, actually I had the manual but I do not know which lead to solder to and where to make that connection from the switch to the relay. This is why I posted the 360deg pics so someone could talk to me like they are telling their 10 year old how to do it. I am clueless when it comes to electrical beyond splicing wires and soldering.

I assume based on the schematic that I jump one wire from the switch to contact 30 and the other to contact 87? BUT where do I attach the wire where it will not interfere with normal operation of the low speed fan when the switch is in the open position? Should I solder the wire to the external male terminals of the relay or to some point on the inside of the relay?
Personally I would "piggy back" the fan relay on the high amp side (pins 30 and 87) IE: Directly connect your piggy back relays pins 30 and 87 to the stock relays pin 30 and 87 respectively with some high amp wire (something that will hold on a 40 amp circuit)

Then you can use your piggy back relays pins 86 and 85 to toggle the circuit with no interconnection to the PCM.


On your piggy back relay you would then send 12v positive through a switch to pin 86 with pin 85 attached to ground to turn the fan on at any time regardless of temp.

What this will do is basically create a redundant high amp circuit allowing your stock relay to function as normal and your piggy backed relay to toggle the fan on even when the PCM is off or the temperature sensor does not signal a high enough engine temp to trigger the fan.

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