I find that my A/C blower will not turn off, even when the ignition is off and the key is removed.

A web search reveals that this is caused by a shorted blower motor control module.

So I am going to replace that part (GM 16173860, ACDelco 15-8548 ).

The part is kind of expensive, so of course I don't want it to happen again.

What probably caused the part to go bad?
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1995 Buick Park Avenue Ultra,
Electronic Air Conditioning (C67)

i dont know specifically but i would pull the motor and make sure the wires dont look corroded and the blower is clean and turns easy. as motors get old they draw more current which can effect controllers, if they are dirty its even more

It sounds like a good idea to pull the motor.

Could you explain more what you have in mind about it being dirty? Maybe the squirrel cage being dirty? Or dirt on the motor causing it to get hot internally? Or debris in the duct work? Not obvious what you mean about it being dirty.

The car has 165K miles, and it is probably the original blower. But I don't want to replace it if it doesn't need it. What if I measure the current draw of the old motor and compare it to the draw of a new one?

all of the things you stated will cause the motor to work harder than normal

i dont recall any of the motors ive seen having lube ports so if its getting hard to turn it should probably be replaced. if you want to compare just keep in mind you have to compare both out in free air because it would draw more installed in the duct. as far as what difference you should be concerned about i dont know ive never had one go that was still good enough to care what the current was

Thank you, JW. I'll try to summarize when I wrap up the repair.