1986 Chevy Truck

First q, is it a digital control panel?If it is are you getting power to the control panel(is it lighting up)if the control panel is working check for a bad ground connection, if not check the fuse.I personally recommend the haynes manual for that year, or the haynes elecrical manual this will help you somewhat understand how to check for power. If your desperate for heat, pull the blower relay (high side) I ran a jumper wire(single wire) from the green/white stripe to the brown wire(hot ) this is what I do on my 88 chevy to get heat(hint wait until the engiine warms up a little. When mine does the same thing yours is doing this is what I do for heat. All my relays are good, the blower works, its just my digital control panel does not work. Intermittent problem!