Quite a few fan controllers have a delay circuit that keeps the fans from coming on immediately when the AC signal arrives. I believe the intent of the delay is to keep the fans off when the compressor quick-cycles for defrost mode, but it'd have the desired effect. I don't have a part number in mind, but I've seen quite a number of them while daydreaming around the web.

 

I tapped into one of the wires that runs out to one of the pressure switches in the AC system. It's switched to ground when the AC switch is on and triggers my fan relay.
Good to know, I'm using Megasquirt to control my fan with the AC power wire spliced in with a diode, so there's no delay.

 

Hey, I don't know if this will give you exactly what you seek, but I used the dual large/small fans from a 96 bonneville for mine. I used a test light to see which of the a/c clutch wires would work as the trigger & T'd into it. I made the harness myself because I enjoy electrical work & I am cheaper than tweety bird. if I don't like the temp, I just turn the a/c on & it starts to cool down fast, but I have not had to do that recently. I still run the stock thermostat. The only parts I had to buy were the fuse holders & the upper radiator hose aluminum T to put the sensor into. I am not personally a fan of the temp probes that stick between the fins. Check out this link but remember, it is a universal set up with a few options. I did the 2nd setup for dual fans.

http://personal.linkline.com/dbarton/FanDiagram/

 

Where'd you get your temp sensor?

 

I pulled 1 that fit out of an audi A4 from a junk yard. I have no idea what the temp rating on it is, but I never overheat.