Adding a switch to my electric fan

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Nick1994

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I'd like to add a manual switch for the electric fan on my Jeep. When out off-roading and driving in the sand, the temperature likes to creep up to 220-230. The fan works great, but it comes on too late for my tastes. I'd like to retain it coming on by itself for when I use the A/C but it cycles on and off and I'd like it to be always on when I want it on.

Anyone recommend a relay kit or something on Amazon or similar? Can't I just run another positive wire from a relay kit to the positive wire on my electric fan, this way it will still kick on on its own?

Thanks for any help.
 
Actually it's easier than you think locate the fan relay in the distribution block in the passenger side of the engine bay you can unclip it and access wires underneath. Then you can simply splice and attach a switch to ground and have it switch on the relay.

Your ground switch should connect to the low current side. Run a single wire into the cabin and then the other side of the switch you add can connect to any metal you can find.

Previous owner of my XJ used the ground on the cig light but any metal will work.

Simplified_relay_diagram_Lg.png



The PCM commands the fan on by grounding the relay low current side you will just be doing the same so with the switch in off position the fan is still controlled automatically
 
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thescreensavers has it completely correct. Everything you need besides some wire and the switch is already in your vehicle. I'm sure there is some "kit" out there for $35 that will claim to do this magic trick, but all you're paying for is the instructions and almost certainly, the cheapest wire and switch available from Asia, which are likely not the proper parts in the first place.

Wire ... you cannot use "Primary Wire" on the interior or underhood, it's for running wire to trailer hookups on the outside of the vehicle only. But, you might have a hard time finding SAE grade wire locally. Best bet is order online.

Switch ... even though you are only switching 12~15V, the contacts need to be more robust than even something switching home AC current/voltage. 12V DC will arc across the terminals far more than 120V AC, and that is a fire hazard. Again, hard to find because cheap junk everywhere, but you want a DC rated switch, versus one only rated for AC.

Lots of people ignore the above, but two things:

One, you may as well know the right way to do it, so you can make an informed choice, and
Two, ignoring the above probably won't start a fire, but "probably won't" is not the same as "won't".
 
I've done something like that in two cars. In my Subaru I added a switch to turn the radiator fan on manually, without affecting the automatic control. I rewired one of the useless dash warning lights in parallel with the fan, to act as an indicator to show whether the fan was on. I was more creative in the Mazda and interconnected the radiator fan with the heater fan circuit. If I flipped a switch and then turned on the heater fan, both motors and the fan resistors were all in series. That way, the radiator fan had three slower-than-normal speeds, which were often sufficient to keep the thermostat from turning the fan on at full speed, and avoided the coolant temperature swings you're trying to avoid.
 
Originally Posted By: Johnny2Bad

Wire ... you cannot use "Primary Wire" on the interior or underhood, it's for running wire to trailer hookups on the outside of the vehicle only. But, you might have a hard time finding SAE grade wire locally. Best bet is order online.

Switch ... even though you are only switching 12~15V, the contacts need to be more robust than even something switching home AC current/voltage. 12V DC will arc across the terminals far more than 120V AC, and that is a fire hazard. Again, hard to find because cheap junk everywhere, but you want a DC rated switch, versus one only rated for AC.



Thanks Johnny you are correct but he/she will only be controlling the coil side.

A typical 40/30 amp relay coil side is only pulling ~0.15 amps at 14v which surely isn't enough to cause arcing, any 18/16 awg wire from local Home improvement/auto store store will be sufficient.
 
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I wired mine up with a dummy relay. The article on cherokeeforum.com is pretty much what I did. The computer can turn it on as needed without setting the check engine light and I can override it.
 
About wire, you may have different terminology in Canada, here in the states "Primary Wire" is named for its intended use on the primary side of ignition circuits. It's perfectly suitable for use under the hood and for wiring accessories like electric fan switches. You are absolutely correct about the need for DC rated switches.

Originally Posted By: Johnny2Bad

...Wire ... you cannot use "Primary Wire" on the interior or underhood, it's for running wire to trailer hookups on the outside of the vehicle only. But, you might have a hard time finding SAE grade wire locally. Best bet is order online.

Switch ... even though you are only switching 12~15V, the contacts need to be more robust than even something switching home AC current/voltage. 12V DC will arc across the terminals far more than 120V AC, and that is a fire hazard. Again, hard to find because cheap junk everywhere, but you want a DC rated switch, versus one only rated for AC.

Lots of people ignore the above, but two things:

One, you may as well know the right way to do it, so you can make an informed choice, and
Two, ignoring the above probably won't start a fire, but "probably won't" is not the same as "won't".
 
You can also upgrade the fan to one from a 97-01 XJ. The 97+ fan has more blades and pulls a bit more air. They can be found on ebay pretty cheap and are a direct swap.
 
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