Two problems related to wiring have been reported for the 1998 Toyota T100. The most recently reported issues are listed below.
Wires to fan connector melted the insulation just short of the connector and shorted out. Pictures of failed wiring are available.
I have a 1998 Toyota T100 4x4 pick up truck. The wiring harness that connects to the blower motor shorted out about two years ago. I had to go to the junkyard and take one out of another model Toyota car to fix it. Since then the wire has shorted out twice more. Basically I believe that the blower is creating too many volts that causes the wires to overheat and melt together. There was no fire but it does smoke when it shorts out. I noticed that Toyota has not issued a recall and this could cause a fire.