Killed my AC compressor and alternator?


Dear Click and/or Clack,

I have a 1971 Chevy Suburban C10 with 33,000 miles on a new 350 engine and rebuilt 350 transmission. I recently installed fog lights myself, and afterwards the aftermarket (“Old Air”) AC system wouldn’t work - the compressor would squeal and bog down the engine. After investigating, I discovered that one of the cables had become disconnected from the heater control. It was the cable that was connected to the hot/cold air blend lever, which also controls the A/C. After reconnecting the cable, the compressor would no longer squeal but would make clicking (and/or clacking) noises. In addition, the alternator had acquired a bit of a whine and would no longer keep the battery charged. My mechanic diagnosed the problem as follows: dead compressor, dead alternator. He thinks it’s cosmic coincidence, but I wonder if by fooling around with the electrical system while installing fog lights, I could have somehow caused the compressor to fail, and if that could have somehow caused the alternator to fail. Or, is he correct and I am simply being subjected to kharmic punishment for owning a 10 mpg, 4,000 lb hunk of rolling steel?


-Jamie in NJ

PS. For the sake of kharmic balance, my other car gets 30 mpg.


Yes it is pure coincidence. The whine in the alternator is a sign of a shorted diode or stator winding. Although this could have been caused by high current draw, it was probably precipitated by heat and long use. If the new alternator is operating okey; not overheating; and not undercapacity since the installation of the fog lights, its failure was just coincidence.

The seizure of the compressor is pure old age and/or lack of oil. Use and time cause wear and corrosion that can lead to locking the compressor and squeeling of the clutch or belts.


Thanks for the reply. The compressor is fairly new - the P.O. had an aftermarket A/C system installed in '03. I did have the truck idling for a while when I was aiming the headlights and testing the fog lights. I don’t remember if I had the A/C on, but I guess that could have killed it. Perhaps I should invest in electric cooling fans…


Ok I’m confused. You replaced the cable that opens the blend door and that made the compressor stop squealing? I don’t see how that would happen. Are you sure it wasn’t just that the blend door happened to be open just a crack, and as air rushed through the crack it whistled? the reason I ask is that it could mean the difference between replacing the compressor or not.

As for the clicking/clacking noises it’s making, go turn the AC on and see if it blows cold. If it quickly switches between cold and hot you don’t have a compressor problem, you have a loss of refridgerant problem. And since your truck runs R-12, you’re gonna be paying a lot of money for it, unfortunately.

Now to the alternator. Disconnect your fog lights and see if the whine goes away. If it does, your lights are creating a parasitic drag on your electrical system, which also explains why the battery dies. It’s actually not hard to create this problem when installing lights, especially if they use a cheap relay. The higher quality lights come with their own proprietary relay and an easy wiring harness that does not require you to know anything about wiring stuff up.