The motor is $40 at Autozone with a lifetime warranty.
The resistor is $20 at the same place.
If anything it sounds to me you have a bad connection or a broken wire- since it works sometimes.
My fan was bad, and it would work and as it got hot/in use for a period of time would slow down until it stopped...
My other car the fan just stopped working altogether.
I would buy both parts, start with the fan. If that doesnt fix it simply remove and switch the resistor.
Easiest way Ive found to do this is put the passenger seat all the way to the back and tilted down. Hop up in the seat backwards and work upside down. Unless your left handed then this should be cake for you.
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-Ryan
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