Originally Posted by kennzz05
where do the two black wires go if you hook a 24 volt wire to the common that is a dead short and will blow the tstat and transformer i suspect you are getting feedback and that is giving you your 24v reading the gas valve needs a common and a power to operate your tstat has red(power)in
(white)power out to gas valve
at the valve you can find your common by traceing it back to where it comes from
Just spent 1+ hour in the basement
... Took both tstats there and hooked them directly to the transformer. My mistake was that I thought R and C on the transformer is what was going to the tstat upstairs. But it was R and W that were going there. So I hooked R and C from the transformer to my new tstat, located W (based on what goes upstairs) and it started working! Will finish it tomorrow and let you know.
Also, the center terminal is actually G (fan, not used) and not C as I thought.