My heater motor keeps running when I shout the car off. I have to disconnect the battery cabal what could the problem be? 1989 Cadillac Eldorado

The blower control Power Module has an internal failure and requires replacement.
Look under the hood towards the rear of the engine bay and locate the Power Module as shown.
Two connectors and three 7mm screws to remove and, with careful manipulation, thread the old one out and drop in the replacement.
Attachment 33534

Thank you, I know exactly were that is I will try that.

Thank you so much it work