Making an aux fan switch--which wire do I use?

oldmustangjunkie · Feb 2, 2009

I saw on old post on here that told which wire was the negative coming from the electric fan relay in an older model XJ. Will that work on my 99 XJ? Can I still cause the fan to come on by grounding the relay? I don't have my XJ here or I would check the wires and tell you what is in the bundle.
Thanks,
Bryan

gradon · Feb 2, 2009

I posted that a few weeks ago("manual switching of aux fan", or something like that). Yes you can run a switch to the relay ground underneath the pdc and engage the fan. Doing this will set a 1491 aux fan cel code. I think if you cut that wire at the pdc(leave yourself a few inches) and install a diode(+ side at ecu, - at relay and then solder your grounded wire at the - end that the switch won't interfere with the pcm. I'll do it sometime this week and report if the code still sets.

ert01 · Feb 2, 2009

gradon said:
I posted that a few weeks ago("manual switching of aux fan", or something like that). Yes you can run a switch to the relay ground underneath the pdc and engage the fan. Doing this will set a 1491 aux fan cel code. I think if you cut that wire at the pdc(leave yourself a few inches) and install a diode(+ side at ecu, - at relay and then solder your grounded wire at the - end that the switch won't interfere with the pcm. I'll do it sometime this week and report if the code still sets.

I'd be interested to see if that works for you... be sure to post up what you find

Making an aux fan switch--which wire do I use?

oldmustangjunkie

NAXJA Forum User

gradon

NAXJA Forum User

ert01

NAXJA Forum User

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