- 1). Check the thermostat settings. This is always the first thing to look at. Make sure it is in the proper conditioning mode, whether it is heating or cooling. Make sure the temperature setting is calling for the unit to come on.
- 2). Check the breaker or fuses with a voltmeter. If there is no power to the load side of the breaker or fuses, check across the line side and the load side of the breaker or fuse. Beakers can trip and yet not appear tripped on visual inspection. Fuses can also blow without any signs. In cases such as these, the voltmeter should show no voltage. If the breaker or fuse shows voltage, the breaker or fuse is not the problem. Move on.
- 3). Reset the breaker or replace the fuse if there is a voltage reading. To reset the breaker, firmly shut the breaker off, then turn it back on. If the breaker is reset, or if you replace the fuse and it trips or blows again, it's time to call a qualified service person.
- 4). Pull the cover off the thermostat. With a screwdriver, remove the mounting screws to the thermostat. This is low voltage. With a short jumper wire, touch the red wire (the power wire) to the yellow wire (the compressor wire). If the compressor comes on, replace the thermostat. If it does not, it's time to call your service person.
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