Armstrong Ultra V Tech 80 with no power


Old 02-08-13, 04:32 PM
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Armstrong Ultra V Tech 80 with no power

I have an Armstrong Ultra V Tech 80 furnace that quit running today. It will not initiate a lighting sequence when requested by the thermostat. There are no blinking codes at the gas valve. It seems as though there is no power. I checked for 24VAC on the circuit board between R & C and between W & C and there is no voltage. I disconnected the transformer input leads from the board and read 120VAC at the terminals. Reconnected the transformer input and measured directly at the transformer output volts. I removed the transformer and replaced a connector that looked loose. It showed 26 VAC on my bench. Back at the furnace, zero volts at the outputs. All connections to the board look clean and tight. Suspecting an internal board connection I tried jumpering from the AC in directly to the transformer, and still zero volts output. Is this an intermittent fault in the transformer, or is there something else I am overlooking? Any help is appreciated.
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Old 02-08-13, 06:44 PM
hvactechfw's Avatar
Join Date: Jan 2011
Posts: 6,245
If you get 0V at the transformer secondary then it is a bad transformer.
Old 02-09-13, 12:41 PM
SeattlePioneer's Avatar
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The most common reason for a transformer to burn out is a short circuit on thew low voltage wiring --- most commonly sorting the thermostat wires to a sheet metal ground.

So I'd use a multimeter to check the resistance between the thermostat wiring and the sheet metal of the furnace and other wise be on the look out for a short circuit.

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