On a 1991 GMC Jimmy the ac heater and vents are not working not blowing air is this the blower if so how much does that run and how easy to fix?
Most likely your problem is just the switch itself that controls
the speed of the fan or a fuse. These are the easiest and cheapest
things to check first. You can get the swithc at a local parts
store or from a GM dealer. If that doesn't work check for loose of
broken wires. It all that fails replace the blower motor. Check the