HOW TO: Control Your Cooling Fan With A Switch

Courtesy of Bradiscool.com

Cooling Fan Override Modification:
(design by Mike Holmes)

Items & Tools Needed:

(1) 30A Automotive Bosch-type relay
(1) SPST Switch
18 Ga. wire
Female spade connectors (for relay & switch)
Butt Connectors or 3M Splice connectors (or solder and heat-shrink if you prefer)
Screwdriver (regular)
10mm wrench or socket
Wire strippers / Crimping tool


First open the hood and locate the fuse panel beside the battery. There is a single retaining clip that holds it in place
that can be removed using a regular screwdriver to pry the center pin of the clip up and out. Next you will need to
remove the single large gauge wire that enters the panel from the battery using a 10mm wrench or socket. This wire IS
live so be careful not to let it touch any metal! Flip the panel upside down and removed the bottom cover with the
screwdriver.......it just snaps off. Using the cover to the fuse panel as a reference, locate the cooling fan relay. There
will be (4) wires going to the relay.......(2) Red, (1) Blue, and (1) Green. Splice into the Blue wire using the 18ga wire
with either a butt connector or 3M splice connector. Connect the other end of this wire to the #87 pole of the relay.
Using the same connection method connect a wire from the #30 pole to the Red wire. You can also connect a wire
from the #86 pole to this same Red wire or use a jumper wire on the relay to do it. Next attach a wire to the #85 pole
of the relay and route it to the inside of the car.....this will be connected to the switch. Mount the switch where you'd
prefer and connect the wire to one of the poles. Next connect a wire to the other pole of the switch and the other end
to ground somewhere inside the car. Re-assemble the use panel under the hood and be sure to re-connect the large
gauge red wire that goes to the battery with the 10mm. Oh yeah, and if you have an alarm be ready with the remote to
turn it off because usually when you reconnect that wire the siren goes off! The next step is .....that's it, you're done!
Flip the switch whenever you want and you're cooling it!


Wiring Diagram

In this Diagram there is a lead shown for a led indicator. Just wire like shown.

Information from Vincent

you realy don't need all of that. You can just run a wire form the left rear post on the fan relay to a switch and ground the other end but if you're gonna use it while the motor is running you'll need a diode