Installed new thermostat but it has no power


Old 02-14-13, 10:27 PM
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Installed new thermostat but it has no power

Connected a new thermostat (honeywell RTH8580WF). plugged the wires in, and the "C" wire in to the thermostat. powered stuff on and nothing shows up on thermostat.

Went into attic to make sure that the "C" power line was indeed hooked up up stairs and it was.

Checked the fuse on the furnace board and it was good.

No error codes being flashed. I have the breaker off for the furnace/ac now, but if turn it on, I hear the fan running on its own.

Just to rule out the new thermostat, I plugged my old one back in and it was not working either.
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Old 02-14-13, 11:40 PM
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It can be tough to see if those automotive, blade type low voltage fuses are okay visually.

I'd check the fuse with a meter or replace it.
Old 02-15-13, 04:32 AM
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It does sound like you have a blown fuse on the control board of the furnace. Check for 24VAC between R and C of the furnace control and at the thermostat. If you have it at the thermostat and the new stat won't power up then you got a bad stat (rare).

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