[artron9]

I bypassed the heater control valve to isolate it from the circulating system. I did this by coupling the two hoses that go to the valve. I figure this will complete the cycle. However, even though the feed hose to the heater core was warm, I don't think the water was circulating through the heater core since the exit tube was cool.
Do you think the heater core is toast? Is there any remedy besides replacement? Am I missing something here or am I on the right track? Maybe the valve function is necessary to allow the water to circulate through the core?