Here is the schematic I created to make my Aux Fan Override. It is essentially the same mod as was found on NAXJA.

I opened the dist. box. Cut the power leads from the Aux Fan, and routed them to the power pins (87 and 30) of the new relay.

I found the power lead that I had clipped to the OEM fan relay in the dist box. This is what used to supply the fan with power and has the big OEM fuse inline. I routed this to pin 87 of the new relay.

The other lead that was clipped from the OEM relay delivers power to fan, this was attached to pin 30 of the new relay.

I put a new power lead on the now clipped OEM Aux fan harness (pin 87) with a 1 amp fuse. There is a +12 dist point on the front of the dist box that works well.

Pin 30 was routed to my switch on one of the poles.

I slpiced into the RUN line under the dash (Black and White large gauge I think) with a 1 amp inline fuse and routed this to other pole of the switch.

The common of the switch was routed to pin 86 on the new fan relay. This allows for selection of what power source activates the new fan relay.

Thats it, works like a charm. Like it says in the diagram I used a (On-On) type SPDT switch, this only lets me choose PCM or Always on control. I can't force the fan off. Like I said before there are many different ways to do this. This is just what I did.


SCHEMATIC1 _ PAGE1 by DortDizzle, on Flickr