Your grand am 99 has had heat for a while but right as winter hit the fan stopped and no heat come out on full blast it only works a little when you are going over 65 on the hwy and idk what it is?

Answer 1

When you say "fan stopped" are you referring to an electric cooling fan? I would check to see if the thermostat is stuck in the open position.

It sounds like the blower motor fan has stopped working. You have heat at 65mph because the air being forced into your car is particially going through the heater core. The heater core takes some of the hot cooling fluid (water) that would go through the radiator to be cooled and "cools' it through the air ducts and into the interior of your car. The blower motor doesn't work. First, check the easiest to fix, the fuse. If the fuse is blown, replace. Next check the fan switch, then fan relay (if so equiped), then the blower motor it self. To check the fuse, look at it. The switch and relay, see if current is going through them. The motor, apply 12v DC to the motor directly and see if it turns. If it's not the fuse, it's most likely the motor. Some cars are a bear to replace the heater motors, gotta remove the whole dash. good luck