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I changed my thermostat wiring from 18 /4 to 18 /5 to provide a common wire. I took pictures of the thermostat and Furnace control board so I could rewire with no issues.

After everything was wired, I tested the thermostat. AC works fine as does the fan. However, I cannot get the heat to turn on. I set thermostat to 72 and house is 68. Thermostat shows "heat on" and furnace shows a steady heartbeat light, but no heat.

I checked the voltage between C and R at both furnace and thermostat and get 24v. Voltage between C and W is like 0.14v. It should be 24v if thermostat calling for heat which it is. I quadruple checked wiring and re-stripped my wires. No change. I tried an old thermostat I had lying around still no change. However, the R wire pulled loose from the thermostat and shorted on the board. The heat came on at that. But I knew I couldn't keep it connected that way.

I re-installed the old 18 /4 wiring and again quadruple checked everything. Wiring looks good per pictures, set screws are tight. AC and fan run fine. Still no heat even with setting thermostat up ten degrees.

Where do I look next?
 

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Post pics of the wire connections of the furnace and thermostat.
 
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..I checked the voltage between C and R at both furnace and thermostat and get 24v. Voltage between C and W is like 0.14v. It should be 24v if thermostat calling for heat which it is.
You sound like you've got some pretty good diagnosing skills. From your description, it sounds like a bad thermostat. Can this thermostat be operated off of batteries? If so, to further diagnose, you could disconnect all of the thermostat wires and use your ohm's/continuity function on the meter to verify. When the thermostat calls for heat, there should be continuity between R and W (your meter should beep). If the stat says heating and your meter no beep, then that means no good.

By the way, you didn't mention what type of stat this is. It's name wouldn't happen to start with a lowercase n, would it?
 
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