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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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2007 impala 3.9l police pkg fan wont come on when ac comes

Customer Question

2007 impala 3.9l police pkg
fan wont come on when ac comes on
compressor just a little noisy - was just a little low on Freon - added some
fan fuse checked good, changed all fan relays
Submitted: 1 year ago.
Category: Chevy
Expert:  Juan Crespo replied 1 year ago.

Hi there. Welcome to our site!

I got to tell you, I'm on your side all the way, but these circuits are very complicated and not easy to diagnose unless you have a scan tool that can read data stream from the onboard computer (PCM).

Now, we could still do this even if you don't have that kind of scan tool, but you're gonna need a good voltmeter and lots and lots of patience. Are you OK with that?

Customer: replied 1 year ago.
that's ok
the kid went back to college with the car
so I wouldn't be able to take readings and relay back to you
unless you had some written down instructions
sounds like the pcm?
Expert:  Juan Crespo replied 1 year ago.

Well, that's the thing; all I've got on the way of "written instructions" are the diagnostic procedures GM technicians use and that would require you to have the same tools and equipment as they do. What I was hoping to do was to "translate" the process based on bits of information you could get using just a multimeter as we went along.

In any case, I would not recommend replacing any parts without first diagnosing the issue - being that this vehicle has the Police options, guessing can get very expensive in a hurry.

Best Regards.