Car has no heat, took to a mechanic, he replaced thermostat, still no heat, plus , now the engine temperature gauge barely comes up. Have felt top, bottom, radiator hoses after warm up. They are warm. Heater core hoses checked, one is not, the other cold. So I think the heater core needs flushed. By doing that, does that have anything to do with the gauge barely moving off the cold mark? Is it possible the thermostat was put in upside down? Engine is the HO 3.5 Also performed the ATC check on the heater controls, no codes came back. Thanks, Brian...