Driving in Florida heat (96) and A/C started blowing a little warm air, then temp gauge rises past 3/4 and red indicator light on dash came on, so I turned off A/C and turned on heater and light went off and temp dropped back down. It appears fan doesn't come on and now A/C cycles off and on and not cooling all the time. Today idling with hood up checking everything, I have 12v at 3 wire plug to fan for radiator, but as temp got above 230 no fan kicked on and I shut vehicle off and almost immediately it sounded like a pressure relief valve blew out underneath and I expected to see antifreeze pouring out, but not a drop. I am thinking high pressure built up in A/C and vented somewhere? Anybody ever heard of such?