electric fans

hello all...Im Steve and I have an 89 xj, 4.0L....i have an electris primary fan that runs off an ajustable switch with utilizes a constant battery power to the fan and turns fan on/off through the negative lead. The factory auxillary fan turns on.off with the positive lead and with the air conditioning unit, but it only seems to turn on (without a/c) when engine temp is up close to red even after replacing the thermal switch. I would like to wie it in tandem with my adjustable thermostat, but due to the negative start/stop I will lose the a/c lead to run with a/c compressor. Should I do that? Or is there any other option? If I run an auxillary swith to the dash it will have to use a negative lead and I may leave it on and suffer dead battery often...

You could use relays to flip flop between what signal you need to activate the fans. Give this a look: http://www.the12volt.com/relays/page1.asp

Remove the positive wire on your A/C relay contact and change it to an Neg lead.

you could use a diode in the circuit so as to run the fan only.that way when the fan comes on it does not kick on the a/c clutch.the 87 90 do this from the factory.aux fan comes on independently of the the temp and a/c function.

Thanks guys for the ideas, I think I'll go with the relay idea Thayer has...

Also just bought hood louvers from RaceAce.com, gonna see if lowering the under the hood temp helps out. I think it will as there seems to a heat trap up there with exhaust manifold under intake and heat rises to the unvented hood thereby not allowing the intake manifold to stay cooler..I'll let you know if I see any differences as well as the acetone I just added to my full tank of gas...my motor only has 20,000 miles after a rebuild so maybe its all slightly cleaner and I can see if there is benefit above the acetone merely cleaning injectors....