Heater Not Heating

[Kneale Brownson]

After the timing belt replacement fiasco with two auxiliary radiator 
removals, the heater on my avant worked fine for the drive from Michigan 
to Colorado, but now I'm getting no heat.

I found the coolant level below the minimum on the reservoir by about an 
inch the first day there was no heat, so I figured it was an air bubble 
in the heater core.  Coolant level has stayed up after the next day's 
driving.  Today I'll test for whether the hoses to and from the core get 
hot.

Most likely the flaps motor?