I have the after market fans also. When frist installed I got the run on also. I in stalled the Rick Mosley (SP) wiring kit with the help of Mike Drew and that stoped that. The kit mounts in the front trunk very neatly and hooks into the your fuse box and routes and reroutes current! It also has a couple extra relays.
I think others make a kit similar to this, and I'm sure someone else can explain what the kit does better then I! I'd look in to a kit like this, it has other benefits also.
Good Luck
Curt
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