Heater blower not working no fan no ac no defrost or heat how do I fix it
Myself on 1998 Cadillac DeVille

where is it located and what else could have caused this problem

Asked by for the 1998 Cadillac DeVille
The blower motor itself is probably the problem. Check the fuses first to make sure one isn't burnt out. Here's the process for removing the blower motor: