2000 Xterra. XE. V6. 3.3L. A/C is intermittently cold and warm. Plenty cold when it works. But especially driving in hot wx (100 deg or more), it will stop blowing cold air. I can turn it off at the dash and wait a few minutes, then turn it back on and it will be cold again. But after a bit the air is warm again. Compressor is not cycling on its own. Likely getting too warm. Have already replaced the thermal control amplifier and A/C switch. Any ideas?