On 12/10/2013 12:16 PM, wrote:
The photos appear to show a heating only thermostat, a very basic
one. For heating with one stage, which is all that tstat is
capable of, you would have 3 wires: power, heat, fan. While there
is no standard that must be followed, typically red is the power,
white is heat, green is fan. That leaves the blue. What it's doing
there, IDK. If you had AC, I'd say it goes to that.

But, in any case, connecting red to white should fire the furnace.
And connecting red to green should turn the blower on. Given
the simplicity of the tstat, I would suspect it's not the problem.

Blue is often the common, or the other side of the transfomer.

I didn't look at Danny's pictures. Simple test
for Tstat is to remove it from the wall. Crank
it cold, and see if there is continutity between
R adn W (should not be). Hot, should be.

--
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Christopher A. Young
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