I went to see an auto air conditioning specialist today. My a/c turns on and off by itself. At first I thought I was low on refrigerant. He hooked up the a/c low and high sides and said they were good - 35 psi low side, and 175 psi for high side, so it meant I didn't need more refrigerant. Also, checked the low pressure switch and that was ok. Even tried testing it with a new switch but no luck. Instead, he told me something quite different - that the a/c clutch air gap had increased due to wear and tear. I guess after 192K the clutch wears out and the air gap increases and when the temp rises past 87 degrees (in my case), the clutch with almost never engage. He said that when it heats up, the magnetic part of the clutch loses its "strength" due to increased resistance especially at highway speed. The owner suggests to replace the entire compressor for about 800 bucks. I said no thanks, it's working fine. The specialist said he'll shim if so the air gap gets closer so it can engage the clutch easier even on hot days. Cost to shim the ac clutch is about 175 bucks. We'll see, I'm scheduled for tomorrow.