Im in New England. Enuf said. The engine comes up to temperature and the heater sometimes is fine. But then it will loose temperature completely and only blow cold air. Then it will go back to working, but lately and increasingly less often.

I've read the FAQs. Somehow I don't think it is a thermostat issue, but it could be. My mind is dwelling on the water control valve. Maybe I'm not using the right term, but a year ago I replaced the 2 heater hoses that go into the fire wall and at some time the plastic valve failed loosing all the coolant. I replaced the valve and didn't pay attention to the FAQ recommendation to get a quality valve. I think I paid 15 for the valve, which look just like the broken one.

Sometimes I get heat sometimes, not. So it seems the problem must be something that changes, but not doing so consistently. Would that be my cheap valve?

Bob Franklin