Engine Revs and then slows, 95 Blazer 4.3

[samahi72]

A couple of weeks ago I started to hear what I initially thought was a bearing going out of my alternator. It has stopped but yesterday when I drove the Blazer I noticed that it would surge and then slow down. When I pulled over and put it into neutral I could see the Tach show the slowing and surging. I could always hear a little click, like a switch, before it would slow down for just a few seconds or so. I am thinking that everytime the clutch engages the A/C unit it slows it down. At least I think it is the clutch engaging (AC is NOT on at the panel). I am not sure why the AC would even be engaging at all unless it is designed to do so? Anyway I was wondering if anybody else had this happen to them. I am thinking out loud that I was going to unplug the power to the AC unit to see if that prevents the cycling of the clutch. Any thoughts?

[72chevelleOhio]

The A/C will cycle in defrost to help clear the windshield...
Some systems (not sure about yours in particular) will cycle when the charge is low, and some will cycle just to keep oil circulated in the system.

[samahi72]

Originally Posted by 72chevelleOhio

The A/C will cycle in defrost to help clear the windshield...
Some systems (not sure about yours in particular) will cycle when the charge is low, and some will cycle just to keep oil circulated in the system.

I guess I could unhook the power supply to the A/C pump and see if that solves the problem. At least that way I will know if it is the A/C or the alternator.

[72chevelleOhio]

I think I would make sure nobody can start the engine on you, pull the belt and spin all the pulleys (except the crankshaft ) by hand. You could find the squeal that way. I know some of the 4.3 's and a lot of the 2.8 engines like to eat belt tensioners. They can have an annoying squeal.

As far as your surging goes, when the A/C compressor engages its a pretty big load on the engine. it will cause a surge in idle.(the engine "computer" is compensating for the extra load)..disconnecting the clutch power wire will really only tell you if the compressor is going bad. You should be able to tell that if your squeal cycles with the compressor.