I just had to restart this topic so it gets seen. This saved me sooo
much work.. I had the new thermo and was ready to dig in until I read
this... It seems to have worked fabulously for me!!!
Press and hold the rear wiper and washer buttons at the same time
until all L.E.D's light, this will put the heater control head unit in
calibration mode, when done 2 L.E.D's (rear wiper and washer) will
alternately and then stop when complete.
If you're lucky, you now have heat!