I had serious blower probs. my climate controls were butchered, so I really really dug into that whole system from under the hood. It sounds like you have a ground problem. When I got mine, someone ran a ground to the motor itself and to the body, other than the original ground thru the dash wiring. I had to tear all the controls and quarter panel out to fix it. Just some pointers, the fan runs all the time, it was a health thing back then, it runs on low due to the potential of carbon monoxide from our gas guzzlers, then the fan switch works thru a series of resistors that increase the current flow to the fan motor, then HIGH clicks a relay under the hood, and it connects the fan right to a wire coming from the alternator for HIGH speed. The ground though comes from thru the dash wiring. It took me many nights to figure this out, mine is a 78 by the way, not certain if yours is or not, but it may be different. Also the HIGH speed uses larger gauge wire, I think it may be 10G going to my alternator. I hope this helps some, this can be a nightmare, but once it works it is really cool to have an old ride with stuff that works properly believe me.