1995 Safari has no heat while warming up or idling. OK, let me tell you my diagnosis,,,, not heater core,,,, not thermostat. Here is why,,,,, in cold weather at idle,,,, the temp gauge does not move up at all,,,, heater blows cold air,,, when driving at road speed, temp gauge moves up, and heater blows super hot. Not a faulty gauge, as it follows the heater air temp,, not a clogged core,, as it blows hot air if temp gauge is up,,so hot fluid is passing through the core, until temp gauge falls back, then blows cool,but will blow hot again at driving speeds, not thermostat, as it is on the 3rd one, none changed anything. heater hoses are not hot at idle,, hot after driving, but will cool if left idling. My thought is,,,,,,,,,,, since it has the rear heater,,, which means more plumbing attached to freezing cold chassis,,,, the idling engine cannot get warm or stay warm with that added cooling of the frame,,,,at idle,,, the motor just can not get or stay warmed up. Can this be true ? Even put a cover on grill, did nothing to change what happens,,,,,,,