How can I make the electric fan stay on?

My clutch fan isn't working as well as it should, and of course that means my Jeep likes to overheat. I'm thinking about replacing it with an electric fan, but whatever I do, I won't have the time or parts to do it for a few weeks. Is there a relay or something somewhere that I can jump across to make the aux. fan say on all the time when the engine is running? It's rather useless when it doesn't come on until AFTER it overheats...

I'm not electrician, but you could just wire a simple switch into it, running to the cabin. hot wire it to the fuse box and have the switch so you turn it off when you turn the engine off.
or you could find a hot wire that is on when the vehicle is running.. and just wire it into that for the time being.

i pirated the power circuit for the factory fog lights that have long since been removed. its already right there and i just needed to get a plug off a junk XJ so it uses the factory plug on the fan still. i used the fog light switch as well but i hasd to run a new power to it because the fog lights only get power when the head lights are on. took about an hour and some playing with the test light.

Isn't there a relay somewhere I can just short across? Where is the relay that normally turns the fan on? If I'm going to do a bunch of wiring I might as well just fix the other problems....

Wow said:

Isn't there a relay somewhere I can just short across? Where is the relay that normally turns the fan on? If I'm going to do a bunch of wiring I might as well just fix the other problems....

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Just put a resistor in the temp sensor and it will send a signal that the fan needs to be on all of the time. I would suggest a 1k resistor.

I wouldn't count on the aux fan to handle all of the load. Replacing the belt-driven fan clutch isn't that bad. Not sure what it takes to replace it with an electric...prolly not too bad.

Wow said:

My clutch fan isn't working as well as it should, and of course that means my Jeep likes to overheat. I'm thinking about replacing it with an electric fan, but whatever I do, I won't have the time or parts to do it for a few weeks. Is there a relay or something somewhere that I can jump across to make the aux. fan say on all the time when the engine is running? It's rather useless when it doesn't come on until AFTER it overheats...

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You don't mention your year. But on the Renix XJ's you can wire a switch in on the fan relay, and it will allow you to turn the fan on and off at will. But it will not interfere with its normal operation.

On the Renix the temp switch in the lower left of the radiator is the piece that turns the relay on and off. A simple solution is to piggy back two wires onto the two wires coming off of the temp. switch and run it to an inside toggle or tip switch. If your lazy and don't want to strip a small piece off of the insulation and solder on your two wires, you can buy splice tap connectors that just squeeze together and prick into the existing wires and have an outlet for the added wire. Your not actually adding or modifying anything, just jumping the temp switch.
I've actually still got a jumper for the temp switch plug tied around the temp switch connector, that has been there for years, just in case.

What year?

On RENIX, the fan runs on its own circuit, with its own relay, and the relay is either triggered by the A/C Request signal or by the Thermal Fan Switch on the driver's side radiator tank.

On later models, there is still a relay, but the TFS isn't, it's a shared sensor (drives the ECU input, which drives the fan relay as well) or the A/C Request signal.

If you want a "quick and dirty" way to get there, unplug the LPCO switch (on the accumulator, below the compressor. Looks kinda like an oil pressure sender) and turn the Aircon on all the time. The clutch will not engage with the LPCO disconnected, but the ECU should still get the A/C Request signal and turn the fan on.

5-90

damo252 said:

Just put a resistor in the temp sensor and it will send a signal that the fan needs to be on all of the time. I would suggest a 1k resistor.

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A 1.0kohm resistor is too little and it'll force the fan to switch on when the coolant temp. gauge has barely reached the 1/4 mark. The correct resistance to use is 4.0kohm (a single 3.9kohm 1/2 watt resistor will do). Here's my write-up on how to do it:

http://www.angelfire.com/my/fan/CTS.html