Question about Air Conditioners
Came back from a vacation and found the downstair thermostat's display blank. I tried all - reset breaker, reseat the unit. The upstair system is OK. The downstair system is not operational. Took the upstair thermostat downstair, and it also went blank. Replaced it back to the upstair wall mount and it is OK. There is a heater/fan in the attic that I have not checked. TIA for some pointers...
If you have a volt meter, remove the thermostat off from the mounting plate and check for 24 volts AC across red (R) and White (W). Then check across Red and Yellow (Y). If you do not find any voltage, follow wire as much as you can all the way back to the air handler that is connected to it. Look inside and see if there is a small Auto (car) type of fuse in the wiring harness. Test and replace if necessary. Jump out the Red and Green terminals on the air handler and replace the door. See if the blower turns on. If so, you have narrowed it to the wiring to the thermostat. If not, you have a power problem and will need a technician.
Posted on Sep 28, 2007
In my case the blank thermostat was indicative of a problem at the furnace. A blown limit switch to be exact due to a neglected filter.
Posted on Feb 22, 2010
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