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?

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1 answer
The AC compressor does run in defrost mode, so you may have been told right! Hear it in floor mode?