91 safari front heater fan help

My 91 safari with 97000 miles has front blower motor issue. i replaced the relay and the fan switch on dash. it will not turn on at all, occasionally will randomly turn on as your driving along. is it possible that the resistor is bad if it will occasionally work?? where is the resistor located on a 91? How many fuses are there for this and where are they located? i checked the 20 amp in the panel by drivers feet and its ok, but is there more fuses? thanks

I have a 2000 GMC Safari and I doubt the GM Engineers were bright enough to fix the problem since I have gone through 2 resistor packs and one blower motor. I have been the sole owner of this van and have put about 130,000 miles on it so far. There was a time that the blower would randomly come on or not and when I jiggled the plug to the blower fan it would start up. I replaced the fan and all was ok. But then the resistor pack lost HI and LO would work on the 2 middle settings. Replaced that and was ok for about 4 months. I recently just lost Hi again. I will wait for it to go further befor I go after the resistor pack again. Anyway the resistor pack is located just to the right of the blower you need to remove the windshield washer resevoir to get to it. At least on a 2000 GMC

On your 2000, the relay in the resistor pack is cheezy and the connector to the resistor pack is cheezy. A poor connection for the high speed blower gets hot and melts the connector on the resistor pack. Bypass the high blower relay and your troubles are finished. Install an external 40amp relay. 20 minutes of work and $5 in parts. If it loses any combination of lower speeds, it needs the resistor replaced.