You may have a problem with worn out brushes in your blower. I have had mine apart 3 times for the same sort of funky intermittent operation. The regulator was replaced once, which did not cure the problem. If it comes on suddenly when you slam or close a door and you've got it on high or auto A/C, then you've got intermittent contact. I'd take a hard look at the motor itself. It's not likely to get any better with time.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.