On Apr 21, 8:19*am, mm wrote:
On Wed, 20 Apr 2011 18:17:50 -0700 (PDT), TimR
wrote:

Do you have any way to feed it 24 V AC? *To terminals R and C? *You
don't need to hook it up to the furnace to check it, just feed it some
jolts. *Maybe a small appliance power supply or charger.

Good idea, or the 24 volts at the furnace itself, or the 24 volts at
the thermostat. *

That's why I always recommend people make or buy a bag of wires with
alligator clips on both ends. *They used to come in lightweight and
heavyweight, but now Radio Shack has only heavy weight, 6 inches, 10
for 4 dollars or so. * Takes 2 seconds to clip one end to the
thermostat wire and the other to the thermostat screw, times 2 = 4
seconds.

I once used a 30-inch long wire with alligator clips at each end to
bypass some problem in my car's ignition harness. *Found the wire in
the harness just before it went into the firewall, and ran the other
end of the jumper wire to the coil. *I meant to find the break and fix
it but that looked like it would be hard, so I just drove that way for
2 more years until I removed my wire and junked the car.

I'm betting 99.9% chance the thermostat is bad. I've never seen
one that powers up on batteries, that then:

displays room temp,
displays set temp which he says he can change
yet, the room temp will not change from 72.

unless he has a sticker with 72 on it, I don't see how it can be
anything other than bad. Still, I would put 24V on it just for the
hell of it.