How to Straight Wire a Cooling Fan to an Engineby William Kinsey
Electric engine cooling fans are used to help remove the excess heat produced by the engine during the combustion process. This heat would otherwise destroy the engine if allowed to remain. Sometimes these fans will cease to function properly. The first thought that usually come to mind is whether the fan has failed. The best way to test it is to bypass the fan's normal circuit and straight wire the fan to the engine.
Locate the positive and negative wires on the cooling fan. Cut both wires and strip 1/2 an inch of insulation off of the ends of the two fan wires.
Connect one end of the 12-gauge jumper wire to the black ground wire of the fan. Connect the other end of that wire to the engine block or any metal part of the car body.
Take the second jumper wire and connect one end of the jumper wire to the positive wire from the fan. Extend the other end of the jumper wire over to the positive terminal of the battery. When the wire touches the positive terminal of the battery, the fan should come on.