My daughter has this Pontiac Grand Am at college about 45 miles from home. She called me and said her blower motor quit blowing in the middle of winter. I had her bring it home on Friday evening so I could check it out. The fuse in the passenger compartment was OK. The 30 amp fuse in the engine compartment was blown. I put a new one in and when I turned on the blower motor it instantly blew again.
I took out the blower relay and it has a corroded post so I replaced it and the fuse. The blower now works on high speed only. It has 5 speeds and only works on #5. What else can I check short of replacing the blower motor? Is there a speed control switch that can be replaced?
Answer: A common cause for only high speed is the blower resistor. It is under the passenger side of the dash, in front of the blower motor, up against the firewall. The circuits burn, and only high works because high is on a different circuit, and does not go through the resistor. If not the resistor, then will need to check for inputs to the resistor from the fan speed switch.
On the connector of the resistor, 1 wire will always be hot, then an additional wire will go hot as you turn the fan speed switch. Speed 1 will make one wire hot, speed 2 will make a different wire hot, and so. Those can be checked with a test light at the resistor connector.
Here is a picture of the blower motor and resistor location.