I have a 1991 Buick Park Ave Ultra Blowers motor runs on high speed all the time even with key off?? The Air Conditioning and heat work fine. It has a 3800 engine.
1) The blower motor relay is stuck, replace it and if the blower motor will only work on high speed, replacing the blower motor resistor. This is if it is has manual Air Conditioning.
2) Replace the Module if car has the auto control for a/c. It has a module no resistor or relay