Posted this on the helpme but no answer. 81 Turbo with a transplant 5 speed. Car runs strong got the boost up to about 5psi. Leaves Civics with large tail pipes and wings behind handily BUT when I run the A/C for about 8-10 miles the engine starts surging. Slows down speeds back up fairly rapidly. Turn the temp control up to hot which disconnects the compressor and problem is still there. Put the climate control in any of the NOT a/c modes and the problem immediately clears up. Checked all the vacuum hoses I could find and they seem sound. Engine acts like losing spark momentarily or fuel is too lean/rich. Seems more like a fuel problem than spark however.

Sure could use some advice on this one I'm baffled. Couple guys said compressor getting ready to seize but 5 HP compressor belt driven pulling down a 180 HP motor I don't think so. Also the belt would show some sort of distress by now. also as noted above when temp control in hot compressor clutch is de-energized and the engine shouldn't even see it.

I would have to say take it to an AC specialist. Not knowing diddly about aircon, I couldn't say otherwise. All I know (and I could be wrong) is that the AC is run off the alternator. Perhaps it is going bad and you are requesting too much juice from it. Just and idea.

david

Actually, aircon on most cars is belt driven...only a few cars, like Toyota's hybrids have an electrical compressor simply so the engine doesn't need to be turning.

An A/C compressor is parasitic, and when you turn it on you may see reduced alternator output or an increased idle just because there's another belt being turned by the engine.

You've absolutely got an odd problem Roger, but I can't really think of a cause right now if you've ruled out a too tight belt and you're 100% sure the compressor isn't crapping out.