The engine is heating fine; the thermostat opens as evidenced by hot hoses to and from radiator. But regardless, that is on a separate loop altogether.

The monovalve makes an obvious thunk when the heat is turned on or off and I don't have the engine running. I've also run it with the the electrical connection off, which keeps it in the open position. I verified it's operation before installing it.

Another thing that puzzles me though, is that after replacing various parts, I did have heat for about a week before it went dead again. I guess the monovalve could be suspect, but why would it work while idling?

I just downloaded the climate control manual from skinnerbox, and it looks like the interior temperature sensors, of which there are several, in fact CAN turn your heat, monovalve, and aux pump all off. But if that were the issue, why does the air delivery still work?

Ben