When I turn on my defroster , I hear a loud noise in my engine compartment . on 1994 Mercury Tracer

I have been told that it could be my air conditioner compressor,but I hear the noise when I turn on my defroster or air circulation . Is the air compressor required for all air functions?

by in Lynchburg, VA on June 09, 2013
1 answer
ANSWER by , June 09, 2013
The AC compressor does run in defrost mode, so you may have been told right! Hear it in floor mode?