guardinocherokee

my truck runs at a temp around 200-210 and my electric fan never kicks on so i want 2 run a switch so i can turn it on and off......if anbodys knows how or has done it please tell me how?

AutobotXJ

Before u get fancy, change your aux fan relay. I had that problem for a year before i finally got around to checking my relay. Does you fan work when the ac comes on?

freegdr

dont think it comes on until like 217

SlackJaw

i'm actually curious about this as well...i want to be able to turn it on when i want

freegdr

dont no if you can do this and still be wired to ac switch might burn stuff up

excess650

OK, I've deleted my original, logical response. In the mean time I've run across a pair of schematics for the electric cooling fan control system(s). Unfortunately, one is marked 1988 and the other 1991, so I can't tell you definitively that they are applicable to 1992 and later XJs.

In both cases the black wire(ground) is run to the fan directly. The power lead to the fan is yellow and black in the 1988 schematic and red in the 1991 version. What I would do is run a wire from an "accessory" position in the fuse box to one outside pole of your switch. You'll have to cut the OEM power lead to the fan(y/bk or r) and the part going to the fan goes on the center pole of the switch. The other part goes on the other outside pole. With the switch flipped in one direction, your circuit is bridged as normal. In the other direction its a manually operated fan, switched by the ignition, and unable to backfeed power into the OEM wiring.

freegdr

but when you have the swich off your going to cut the circut for it to work with the ac correct?

excess650

You posted your question prior to my editing the original post, but regardless, the answer would be yes. The circuit will operate normally(as originally designed) in one position or manually in the other. The AC would trigger the fan in one position or the fan would already be running in the other position, so no problem either way. (Haines manual as supplier of schematic for 1988 and 1991 as mentioned in previous post)

freegdr

i see this working in the 88 because there no coolant temp sensor involved with the fan circut would this affect the 91 coolant temp sensor function which also turns on the fan

excess650

Yes, the manual switch would trigger the fan to run whether the temperature sensor thought it should or not. When toggled in the other direction the system would operate as originally designed.

excess650

I've just returned in from braving the heat. As verified on my '96, the harness connector to the fan has black and green wires. These plug into the fan with its black and white wires. Black from the harness shows continuity to ground with the ignition on or off. The green wire shows no continuity to ground, and no voltage unless triggered by the A/C or the temperature sensor. In this case I'm reading 13.65V.

Under the dash in the fuse panel is a socket marked "power accessory" with the ignition off, it shows no voltage, but with the ignition on, it provides power.

As already described in the earlier post, the switch wiring will work. What seems to be consistent between the 1988, 1981, and 1996 is that the black wire is ground.

freegdr

i mean if you cut the wire to the fan will it affect the other things the temp sensor operates to other systems

excess650

If you cut the wire to the fan, it only disables the fan. The black wire is constantly ground to the fan. The power wire to the fan only receives power after having been activated by the temperature sensor and/or AC switch. I had my fan unplugged, wires effectively cut, to check for voltage with the AC running. The fan is at the end of the line.

freegdr

kool now does the op under stand it will work

freegdr

hey he left