1987 Chevy El Camino blower motor

I cannot get the blower motor in my el camino to work for more than two weeks at a time! I used to work for Ford and our shop guys were pretty sharp. The last time I took it to them they said there was a bad wire at the fuse box. They repaired that and it lasted about two weeks and quit agian. The thing that bothers me is the voltage meter inside the car. When the blower motor is running it is constanly bouncing between blue {ok} and red on the low side. What are we missing. I have replaced the seleonid, and the relay, plus I know the motor is good.