Radiator Fan Override Switch (The Easy Way)

[XJ_Rudolph]

(apologies to fyrfytr for cluttering up the thread)
Okay, poking around with the meter, doing some googling. The light blue wire isn't ground, it's power. Ground is black, and unswitched. The relay in the PDC, when energized, puts 12V on the blue wire, fan runs. Taking an educated guess here, but is this how you actually wired it up, Charles? (and sure enough, the PCM doesn't monitor the fan, just the control ckt)

Switch off, stock power wire connected to 87a (NC) contact, wire from fan connected to 30, fan runs only when PDC energizes.
Switch on, battery power on 87, fan on 30, stock power wire held open, fan runs constantly.

Have I got it right?

Looks like I might be bringing this thread back from the grave...but does anyone have a link to the relay needed for this diagram? For some reason I cant find a DPST relay (if thats even the correct one) thats not 30$. Thanks guys!

 

[paddlernate]

This is a simple stocked item at Radio Shack. I think mine was like $9.

 

[XJ_Rudolph]

This is a simple stocked item at Radio Shack. I think mine was like $9.

Do you know what its called exactly, like the name of the relay? Thanks!

 

[831_xj]

lol like... "20amp relay" It's just a basic relay you put female fittings on.. same ones you'd find in your pdc

I went the even easier way with just the 6 pole switch from Napa.

 

[Lowrange2]

It's just a relay. Any ole' 40A relay will suffice. ANY parts store, radio shack, walmart, etc will sell them.

 

[XJ_Rudolph]

It's just a relay. Any ole' 40A relay will suffice. ANY parts store, radio shack, walmart, etc will sell them.

Dang, i thought it was a super special one because when the switch isnt on, the regular control has to be connected. Then when you flip the switch, it disconnects it from the AC and temp sensor.

 

[XJ_Rudolph]

It's just a relay. Any ole' 40A relay will suffice. ANY parts store, radio shack, walmart, etc will sell them.

dang im so stupid....iv been thinking of 4pin relays the entire time....it is just a generic 5pin relay.

 

[fyrfytr1717]

Yes, probably the most common 5 pin relay. Be aware however that there are also 5-pin relays with dual 87's instead of an 87 and an 87a. These are typically used for wiring a pair of headlights (one to each 87 pin) for example and are fairly common as well. Just make sure you get one with an 87a pin for your intended application.

I usually order Hella branded relays from Susquehanna Motorsports for about $7 each (last time I bought them), if you were curious...

 

[XJ_Rudolph]

Yes, probably the most common 5 pin relay. Be aware however that there are also 5-pin relays with dual 87's instead of an 87 and an 87a. These are typically used for wiring a pair of headlights (one to each 87 pin) for example and are fairly common as well. Just make sure you get one with an 87a pin for your intended application.

I usually order Hella branded relays from Susquehanna Motorsports for about $7 each (last time I bought them), if you were curious...

Ok cool thanks!!!

 

[zak7711]

Thanks a lot for the good write up. Better than what I received in the rad fan package.

 

[spinaldex]

Based on what I've read, I thought the electric fan in an XJ is based around the ground wire not being connected until its passed through by the thermostat control. Couldn't you just splice in to that wire right at the fan, and then run a toggle to a switch which is grounded? On = grounded and the fan runs, off = still running under normal control from the truck.

??

 

[Veeb0rg]

No, splicing at the fan would do no good. The ground that's not connected is at the relay in the PDU. Connecting to the ground wire for the relay with a toggle to ground will allow the functioning as you said. Newer 97+ jeep don't like it however and may throw a CEL light, the older ones don't care.

 

[spinaldex]

Has anyone done this a high amp toggle switch to apply power directly to the blue wire going to the fan on a 00-01 to see if does a CEL? I bought a relay and the darn thing isn't labeled so I have zero clue which one is 87, 87a, 30, etc. But that got me thinking why not just run a toggle to simplify the whole thing?

 

[Miller88]

If I'm reading it right, yes, a few people have. It causes the check engine light to come on.

I just went to the junkyard and grabbed a fog light relay out of another XJ to use for this. It's labeled, was $.50 and is more than up to the task of activating the real fan relay.

 

[MrSimon]

I just used the write-up on the first page on my 2000. It was easy and works great. Thanks for the write up!!!

I took me about half an hour to do the whole thing.

 

[fyrfytr1717]

Glad to see people are still finding this thread useful, 6 years later! The override is still working as intended on my XJ...

 

[gradon]

Today I was diagnosing my 2nd e-fan not working and it turned out to be the fuse instead of the relays. Switch still works and no cels. I rec this thread on occasion. Thanks again.

 

[MrSimon]

I have a wiring question.

Since I am feeding the new fan relay a GROUND signal from the in-cab switch, I don't have a 12v source going to the switch (standard five pin rocker switch).

I'd like to wire the switch up so it illuminates when I turn on the headlights like other switches. My problem is that the pin where I usually feed the switch a 12v signal is currently used to feed the ground signal.

How do I get the switch to light up?

 

[mechbullxj]

(apologies to fyrfytr for cluttering up the thread)
Okay, poking around with the meter, doing some googling. The light blue wire isn't ground, it's power. Ground is black, and unswitched. The relay in the PDC, when energized, puts 12V on the blue wire, fan runs. Taking an educated guess here, but is this how you actually wired it up, Charles? (and sure enough, the PCM doesn't monitor the fan, just the control ckt)

Switch off, stock power wire connected to 87a (NC) contact, wire from fan connected to 30, fan runs only when PDC energizes.
Switch on, battery power on 87, fan on 30, stock power wire held open, fan runs constantly.

Have I got it right?

This is how you'd wire your aux. fan, it uses a SPST switch. I've a SPST switch that has three terminals to power the circuit. It's a Daystar KU80011. No.7 is the ground for the lamp, No.3 is power out, and 2 is power in. Using a switch like this the lamp lights when the fan is turned on. Having a switch light when using the cars lights you would have to have the switch spliced into the headlamp switch directly. Not sure how to wire with your particular 5 terminal switch.

 

[fyrfytr1717]

I really wish the above referenced wiring diagram had never been posted in this thread, it really did clutter it up and causes confusion as it is in conflict with the idea/intent of this thread.

That being said, you can still make your switch light up with the rest of your instrument panel so long as your switch provides for that option. It works fine with my Carling switch. The main light illuminates when the fan turns on/off, and the secondary light turns on/dims with the rest of my instrument panel. Can you provide a pin out diagram of your switch?

One issue you may have however is dependent on the type of bulbs in the switch. Incandescent bulbs don't care if the + and - are switched so you can just ground the positive pin and apply the dimmer signal to the negative pin. If you have LEDs in the switch on the other hand, you may be out of luck as LEDs don't let current flow through backwards.