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Our home central air conditioner system will not run. The thermostat is indicating a (- AC) on the screen.

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  • montereykh Apr 09, 2011

    Thanks for the info. The fuse on a circuit board inside the interior unit was blown 5amp.
    I replaced it and the new one blew. Whats next?

  • montereykh Apr 11, 2011

    Thank you for the help, I have not found the actual short yet.
    I will post the results when successful


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Ok, I need to make sure that the power to the outside unit is on both at the breaker panel as well as at the outdoor disconnect.While you are checking, make sure the power is on to the indoor unit. Now make sure the filter is clean to allow air circulation. If the thermostat is calling for ACt, the fan at the outside unit should be spinning. if you hear just a humming, take a stick and see if you can spin the fan. It may be rusted and not able to spin. If it still won't spinn and you cannot hear a hum, check the fuse in the air handler unit. It may be located on the PC Board or in-line of one of the wires. If still no luck, time to call your local AC tech.

Posted on Apr 09, 2011

  • Chandler Ede
    Chandler Ede Apr 10, 2011

    If the internal fuse keeps blowing, you either have a short in the wiring or a bad thermostat.


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It sounds like your thermostat is calling for AC. Since we are just coming out of the winter months, there is a list of things you need to check:
1- Make sure the breaker in your panel for the AC unit is on.
2- Outside where your A/C unit is, there is normally a power cutout or breaker. Make sure it is on.
3- On your thermostat, make sure that the fan is set to ON and not AUTO or OFF.. AUTO is in most cases reserved for the furnace.
4- Make sure your furnace/oil burner is still on, (not running, just that it still has power) and the emergency switch and breaker is also on. The fan/blower is interlocked through the furnace, and usually powered on the furnace circuit.
-If you still do not have A/C, let me know and we will follow through. 99% of the time, it is one of the above.
Thank you for using FixYa

Posted on Apr 10, 2011

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