I'm having the problem described by the author.
-Blower motor on high, stays on for a few minutes after turning off the engine.
-Temperature gauge at 0
I see some people are replacing parts and finding that the issue is still happening. I haven't yet replaced any parts, but I noticed that disconnecting/reconnecting the battery "fixes" the issue temporarily for me. If I disconnect and reconnect the battery, and turn the car on again, the temperature gauge immediately shows the temperature (above 0), and the blower is at a normal speed. I think that there may be some bad software going on in addition to whatever hardware is intermittently failing for me. If you replace some parts, make sure to disconnect/reconnect the battery to reset your computer state.