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Can you identify this noise?

My car is a 98 Mazda 626, V6, manual transmission, 130K miles.

The car has lived in WA, MA, OH, and this summer moved to south FL. In those first three states, the AC was hardly ever used. Since coming to FL, it has been on almost all the time, and has run amazingly cold, considering its age.

One day in Sept., while on the highway on a 90+ day, the air turned hot for a couple of minutes. I was almost to my exit, and by the time I was pulling in to my neighborhood it was cold again. At that time there were no noises at all, just a change in the air temperature.

The next 2 times I started it, it took a couple of tries, but since then it has started normally. Had it looked at (Firestone–we don’t have a mech. here yet) and they could find nothing wrong.

When I run the car with the AC off, there is a noise (not belt screech, but sounds like something rotating) you hear more inside the cabin than out. When the AC is switched on it changes (reduces) the noise noticeably. I suspect the noise has something to do with the AC because of this.

All belts, including timing belt have been replaced in the last 25K miles. The engine light has not come on at any time since this started. It drives as it always has; mileage and power have not changed.

Any ideas what could be causing the noise?

This summer my '96 Didge van (with 118k miles) developed a screeching, rattling sound under the hood. It turned out to be the A/C Clutch. I tried to buy a clutch but every place I went they wanted to sell me a compressor with clutch. ($300 +). So I went to my son-in-law’s recycling busines and he gave me a used compressor and I took the clutch off and put it on mine. Cost 00, time spent, about 30 minutes. I would bet you have the same problem.

Based on your description I would suspect the AC compressor clutch. The clutch allows the compressor pulley to spin freely when the AC is off, and engages the compressor when you turn the AC on.

Thanks to you both (EllyEllis and mcparadise) for your responses. I do not work on the car, but listen to the ct boys faithfully, and suspected the same thing. Now I get to try to find a mech and get it taken care of.
Thanks again!

They will try to sell you a compressor!!