why does heater/ac fan not come on at times. Am perplexed. not best time of year on 2001 Cadillac DeVille DTS

one day we drive and the heater works fine, next time, nothing.

1 answer
I had the same trouble it would sometime go on and off when I hit a bump. Turned out to be the blower motor located under the dash on the passenger side (after you remove some panels etc.) Good luck