Here's one I'v been a mechanic for forty years.state lnspector.I took and replace heater core thermo had it flushed revise flush and I still got no heat replace all hoses checked vacum hoses.no heat.whats next a head gasket.everything clean and no leaks I'v had the jeep since new

Thoughts:

Check for heat at the heater core's incoming and outgoing hoses. If there's heat, focus on the blend door and blend door actuator. If the SUV has Electronic Air Temperature Controls (EATC), run the diagnostics. Just running the diagnostics will often reset everything. Also, read your Owner's Manual on how to properly refill the radiator and purge the system of air.

Have you had overheating problems?

Never had a heating prob before till I replaced the resover tank.and added new anti frezz

All my heaters doors open an shut when the contorl knob is being turn to the opening position.I'm dum founded on this heater crap just trying to get heat thanks guys for your help I'll keep pokeing I should fine something on it. Thanks again guys

Still no heat I'm going to wait till spring to fix it .thanks guys.
I'v got a 2002alreo by olds.my evap light comes on don't have a clue on this .can u tell me what's wronh.