Secondary or auxialliary fan not operating AC on.The fan is good because it comes on when the AC is on. I've replaced the passenger side switch in the block with a Hypertech 166 and the relay by the master cylinder. The fan still doesn't come on due to high temperature. I put sealing tape around the threads of the Hypertech switch, could it be keeping it from grounding? Does the temp switch in the front of the intake have anything to do with the secondary fan via the ECM? I've read the posts and thought that one mentioned it for a 1990, which is just like a 1991 and 1992 I think. Any help is appreciated

 

Sounds like you did everything right. The switch on the front of the block does nothing related to the secondary fan, you changed the right switch. I believe if you ground out the wire to the secondary switch the fan should come on. If it does, the switch is bad.