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cheap jeep
11-07-2009, 05:27 PM
I wired my electric fan today,now I can have it run whenever I want. Pretty easy,I used a light or horn relay,wired it to a switch inside from a circuit that is only hot when ignition is on.Relay was $4.40 from Advance Auto.

BlueXJ
11-07-2009, 05:49 PM
Show us the write up or it didn't happen.

cheap jeep
11-07-2009, 07:40 PM
I bought an off/on toggle switch,and a light/horn relay. I ran 1 wire from the switch to a circuit in the fuse block under the dash,that is only hot when the key is on. The other switch wire to terminal 86 on the relay,I ran term.85 to a ground,term.30 to the hotwire side of the fan(mine was the white wire),I ran a wire from the battery to term.87.That completed the wiring,Now time to test,key on. switch on-fan runs,key on,switch off-no fan,key off,switch on- no fan.This way I can't forget to shut it off and come back to a dead battery.

Mudderoy
11-07-2009, 10:18 PM
I bought an off/on toggle switch,and a light/horn relay. I ran 1 wire from the switch to a circuit in the fuse block under the dash,that is only hot when the key is on. The other switch wire to terminal 86 on the relay,I ran term.85 to a ground,term.30 to the hotwire side of the fan(mine was the white wire),I ran a wire from the battery to term.87.That completed the wiring,Now time to test,key on. switch on-fan runs,key on,switch off-no fan,key off,switch on- no fan.This way I can't forget to shut it off and come back to a dead battery.

And it runs normally as well, I mean via the temp sensor?

cheap jeep
11-07-2009, 11:11 PM
I spliced the wire in at the fan, it should run as normal. The relay won't let it backfeed,but I have never heard mine run,I haven't had it very long so no hot weather.

BlueXJ
11-07-2009, 11:17 PM
How about a few pics. You did an excellent job explaining it but a few pics would make it clear to even me.

cheap jeep
11-07-2009, 11:42 PM
I don't have a digital camera.When I took CDL training the tractor we drove had a electric fan clutch,it worked thermostaticly and it had a switch also. That way if you left the truck idleing for a few minutes or overnight,the fan stayed locked on so you didn't have to worry about it overheating.Plus I think it would be better to try to keep the heat down,instead of trying to cool it down,once it got hot. Just my idea.

BlueXJ
11-08-2009, 07:57 AM
OK I agree with you. Wish the mechanical fan had a lockup switch instead of just the thermostatic control.

xj4life2
11-23-2009, 10:50 AM
This is a real good wirte up on this
http://www.olypen.com/craigh/auxfan.htm

Mudderoy
04-07-2010, 02:28 PM
http://www.jeepforum.com/forum/f11/auxillary-fan-override-switch-write-up-pics-811703/

Mudderoy
07-12-2010, 02:34 PM
Please keep in mind that this is a 1998 Jeep Cherokee. These pictures should be correct for that model year, but may be different for others. The color of the wire seems to be the same, dark blue/violet.

I didn't get as much done this weekend as I had hoped to, but I did get my auxiliary electric fan connected to my overhead switch box.

I located the dark blue/violet wire in the harness. I had to dig around to find it.

http://lh3.ggpht.com/_b0ViaGso2Ko/TDtriPQfBBI/AAAAAAAAAUE/8jrSlKcX8qs/s912/2010-07-11%2014.27.19.jpg

http://lh4.ggpht.com/_b0ViaGso2Ko/TDtq7GKgy2I/AAAAAAAAAUA/0EVgQpEmd0U/s912/2010-07-11%2014.27.51.jpg

http://lh5.ggpht.com/_b0ViaGso2Ko/TDtqkRngoJI/AAAAAAAAAUM/ZRb65auBVFo/s912/2010-07-11%2014.28.27.jpg

I cut the wire, then verified it was the correct wire by starting the engine and turning on the A/C. The electric fan did NOT turn. I then touched the two halves of the cut wire together and the electric fan came on.

I used this diagram from the link at Jeepforum above....

http://i681.photobucket.com/albums/vv171/90XJBeast/Offroading/XJ_Auxfan_wir1.png

...more to come...

Mudderoy
07-12-2010, 04:50 PM
After do a little more research I think I understand why the above wiring is giving me a "Check Engine" light.

I found a diagram similar to this on NAXJA.

http://xjtalk.com/images/special/auxfanbypass.jpg

The signal from the PCM (computer) is a ground. So to turn on the aux fan all you have to do is cut the Dark Blue / Pink (DB/PK) wire and ground the part of the wire that goes to the fan. The problem is that the PCM sees an open circuit and that throws up the code. The trick is to keep the PCM happy. Wiring it to the relay in this manner completes the circuit to the PCM when the PCM asserts the ground. This energizes the poorly drawn COIL in the relay when then pulls the switch from open to closed. The fan line is grounded and the fan turns on. So at this point we have it working the way it was working BEFORE we cut the DK/PK line.

The DB/WT (Dark Blue / White) line is a line that has 12 volts on it, that you can use. It is in the same wiring harness as the DB/PK line.

** I'll add; Even though the ground running from the switch to the efan was not shown to be fused, or a certain size gauge wire used, I believe it should be fused. In fact, at least in my case, it probably should be switched by a relay. The current is carried in both the positive and negative sides of the wire. So when I hit the efan bypass switch ?? amps is flowing through the ground wire! My switch is rated at 16 amps, but I'm sure the wire I am using isn't. I need to size the fuse on this line to slightly more than what the efan is rated at, plus I need to replaced the wire going to the switch with the same current rating! Right now I'm just not using the bypass switch.

Now to accomplish the bypass all we have to do is add a switch that sends a ground signal to the fan, completing the circuit and turning the aux fan on.

Use 18 gauge wire for this. I have to rewire my stuff, so you can wait and get a confirmation that this indeed does work and doesn't issue a "Check Engine" light. It makes sense to me how it works, and I believe that this is how it needs to be done.

Mudderoy
07-12-2010, 10:27 PM
Ok I rewired my relay and switch to match the diagram from the prior post. Works fine and the "Check Engine" light cleared.

The only thing that wasn't the same was the DB/WT wire. That was for a 1999 Jeep Cherokee. I had to poke around in the wiring harness to find a 12 volt line that was on with the key. I found one that was only on when the engine was running, which is perfect for my application. On my 1998 it wad dark blue orange. DB/OR?

You may have to find a good switched 12 volt source in your wiring harness. I just pressed the volt meter prob into the wire. I would recommend a good work glove so when the probe slips off the wire...

Dirt Dogg Rydas
07-13-2010, 03:53 PM
I tried the write-up on jeepforum on my '94 and It doesn't work when I attach it to ground but it does on +12.
Does anyone know if that's the way it should be?

Mudderoy
07-13-2010, 03:59 PM
Ok I rewired my relay and switch to match the diagram from the prior post. Works fine and the "Check Engine" light cleared.

The only thing that wasn't the same was the DB/WT wire. That was for a 1999 Jeep Cherokee. I had to poke around in the wiring harness to find a 12 volt line that was on with the key. I found one that was only on when the engine was running, which is perfect for my application. On my 1998 it wad dark blue orange. DB/OR?

You may have to find a good switched 12 volt source in your wiring harness. I just pressed the volt meter prob into the wire. I would recommend a good work glove so when the probe slips off the wire...

Looks like the diagram above needs a diode to protect the ECM from coil field collapse. I'll add that to the diagram after I add it to the circuit and confirm.

Mudderoy
07-14-2010, 08:38 PM
The "Check Engine" light came back, so let me work on this a bit more before I deem it "WORKING".

http://lh3.ggpht.com/_b0ViaGso2Ko/TD5lz8TRXxI/AAAAAAAAAUs/Wr4cqTcPRE4/s640/2010-07-14%2019.42.41.jpg

http://lh4.ggpht.com/_b0ViaGso2Ko/TD5l6TPAf-I/AAAAAAAAAUw/dXRzYQf6nT4/s800/2010-07-14%2019.43.29.jpg

4.3LXJ
07-15-2010, 09:50 AM
Switches are looking good Muddy. I guess I am going to take that plunge too. I added it up and I couldn't believe I would need 10 switches :eek:

Mudderoy
07-15-2010, 10:22 AM
Switches are looking good Muddy. I guess I am going to take that plunge too. I added it up and I couldn't believe I would need 10 switches :eek:

lol yep. I think most people just add a switch here and there as they go, but I knew I didn't want switches all over the place. I wanted them grouped together and I didn't want something that looked like a shoebox attached to my headliner. I still have some problems with this switchbox, but I'm not done with it yet. :thumbsup:

4.3LXJ
07-15-2010, 11:08 AM
Most scratch built stuff takes real time.

Mudderoy
07-15-2010, 11:15 AM
And I'll add, I think everyone knows this but, I don't care what you put on your jeep, or your head for that matter. Shoe boxes included. I just didn't want it on my Jeep. :cool:

Mudderoy
07-30-2010, 12:16 PM
The last circuit diagram works but DOES cause a "CHECK ENGINE" light to be displayed. It comes and goes. Stay tuned, I will figure this one out. (OBD II code 1419)

Oh I'll add the "CHECK ENGINE" light comes on even when NOT using the bypass switch!

4.3LXJ
07-30-2010, 01:56 PM
Tony. If I was doing this, I would wire in a separate circuit with a separate relay operated by the switch that runs parallel with the stock circuit. That way, either circuit could operate the fan or even at the same time. It would be seamless. The relays would prevent feed back also.

Mudderoy
10-16-2010, 09:30 PM
The last circuit diagram works but DOES cause a "CHECK ENGINE" light to be displayed. It comes and goes. Stay tuned, I will figure this one out. (OBD II code 1419)

Oh I'll add the "CHECK ENGINE" light comes on even when NOT using the bypass switch!

Update:

I disconnected the positive going to the relay and connected it directly to the battery positive. The "CHECK ENGINE" has gone out. I suspected the PCM didn't like the 12 volts coming and going. If it stays off for the next few days, a week, I'll report back and probably create a new thread on how to install a electric fan on 1997+ XJ bypass switch.