Just finished header install and i also had to replace a broken fan switch that was in the passenger side head. Whenever i turn the key to the ON position both of my electric fans come on...Also a very very short time later my thermostat opens up. Its a 160* but it shouldnt be coming on this soon. The fan switch is in all the way and the plug is too. Whats the deal???

 

Do the fans come on when the switch is disconnected?

 

I havent checked yet, been so busy with the header install, plus i kind of like the fans on, i just dont want to wear them out.

 

Some cars have both fans come on with AC pressure, some have NC switch, some NO. If the wire was disconnected it can make both fans run all the time. Not sure on the 91 but look for the pressure switch on the passenger side near the frame rail, small AC line.