...get as hot as the inlet hose.? What is my most likely problem as to why my heater doesn't get hot. It get a little warm for a minute but then stays kinda cool. Flushed the system, that didn't help. My heater core doesn't leak and with a garden hose I can flush it and make it flow water but fully hooked up with the outlet hose off it only trickles from the outlet hose. Could there still be a clog or is it likely its just a vent door getting stuck? The only controls wanting to work are the dash vents and defrost, floor control won't work