Installing Fan Override Switch

[TractorHauler]

I have a 2003 IH 9200 which is a former Wal-Mart truck and of course they don't have a fan override switch. I am wanting to put on in so when I am idling and running the AC I can leave the fan on and save my fan clutch. Question is, where do I hook power to? I know I need to install a switch and have a hot wire coming to the switch, just need to know from the switch, where to take the other wire to?

[Shnerdly]

It depends on the fan that you have.

Most of the trucks I have worked on have an air valve that actually controls the fan and the valve is controlled electrically. Normally they have constant ignition power to them and are controlled by ground through many things including the AC high and low limit switches and the computer.

If that is the case, locate the valve by following the quarter inch air line from the fan clutch to the control valve. Then unplug the electrical connection to the valve and see if that forces the fan run continuously. If it does, you need to determine which wire is power and which is ground. Run two wires from the dash switch to the valve and use them to interrupt the ground wire to the valve by cutting the ground wire and connecting each end of the cut wire to the two wires you ran from the switch.

[heavyhaulerss]

I did mine this way. found the fuse that controlled the fan. then cut the wire going to it & wired a toggle switch to the 2 ends. the toggle switch should be in the on position at all times for the fan to stay off. since a blown fuse triggers the fan to come on, the toggle switch simulates a blown fuse when in off position. put this on my old wal-mart truck & it has worked flawless for over 11 years now. this also save on the solenoid wearing out witch cost $100.00 more or less. with my fan fuse being less than a ft away from my dash panel it was real easy.

[heavyhaulerss]

I did mine this way. found the fuse that controlled the fan. then cut the wire going to it & wired a toggle switch to the 2 ends. the toggle switch should be in the on position at all times for the fan to stay off. since a blown fuse triggers the fan to come on, the toggle switch simulates a blown fuse when in off position. put this on my old wal-mart truck & it has worked flawless for over 11 years now. this also save on the solenoid wearing out witch cost $100.00 more or less. with my fan fuse being less than a ft away from my dash panel it was real easy.

I will say on mine, I cut the wire 4-5 inches from the fuse itself. ran both ends about 8-11 inches to each end of toggle.

[Windwalker]

On mine (back when I owned my own), I got a couple of the connectors from a dealer, and plugged in a short jumper cable (just 2 wires), and one side went to a switch that shut the power to the solenoid off. Open the switch and my fan was on continuous. Sure beat pulling the plug when I wanted it to stay on.

[TractorHauler]

Thanks for the information guys! Guess I have got something to do this weekend.

[allan5oh]

The other posters are right, you have to find out what kind of fan clutch you have. My truck needs 12V to turn off the fan, others need 12V to turn it on. The former is better because it's a failsafe and all you need to do is cut the power before the relay.

[Shnerdly]

Allan5oh is correct that some require power to be on and some require that power be removed to be on. The most common is the one that requires that the power be turned off to turn the fan on.

It's important to know that the newer the truck the more connected or integrated the computer is to the engine control functions. The fans that require power to be taken away to turn the fan on can post engine and/or computer errors if you actually remove or interrupt the power to the solenoid that controls the fan. The devices that control the fan on these trucks, control the ground to the solenoid so that is how it should be done to remove the possibility of reported errors in the computer