no heat one hose hot one cold
Clogged heater core. Try a cooling system flush.
changed heater core
Valve to open flow to core then, I would have answered the same as tenspeed, he is right, but if you changed the core did you check the valve that controls the flow?
Change your hot hose and change your heating sensor and if the don't work you, will have no choice but to change the heater core check all your main fuses that's the big ones under hood
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