Ac trouble


Old 06-06-14, 10:30 AM
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Ac trouble

Tech comes out last week. Replaces low voltage fuse. Works fine for a week and quits. Now I know where the fuse is located, so I go the auto parts store and buy a pack. Replaced the fuse and it immediately blows. Short somewhere but I don't have a clue where to look. ideas?
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Old 06-06-14, 10:48 AM
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The fuse protects the low voltage (24VAC) control voltage circuit. There is a 24VAC transformer which supplies power to the thermostat. When the thermostat calls for cooling, a relay in the thermostat closes, sending the 24VAC to the outside unit (compressor/condenser).

With the thermostat turned off (not calling for heat or cooling), does the fuse blow when replaced? If it does, then the short circuit is probably somewhere indoors, between the transformer and the thermostat (includes the air handler). If the fuse only blows when the thermostat calls for cooling, then the short circuit is likely in the wiring running outdoors. Perhaps an animal chewed through the insulation.

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