I have an older Kenmore a/c / propane furnace and air handler. This house was a foreclosure and I have had it for a few months, so I do not have much history on the unit or installation info. Immediately on getting possession of the property (it was cold out), I discovered that the air handler blower would turn on apparently randomly regardless of what the thermostat was set at. Now that it is hot out, we are having difficulties with a/c. I am hoping somebody can point me in the right direction. It seems to be an electrical issue to me.
So...this is what -
The air handler and compressor will run and keep the temperature as set on the thermostat. It will continue to work fine for several hours.
At some point, the compressor unit will not come on but the air handler will, then the air handler will not shut off despite turning the thermostat to the off position. The only way to stop the air handler (that I know of) is to turn it off at the breaker.
Once the breaker is off, turning the breaker back on will immediately kick on the air handler but not the compressor, regardless of the thermostat setting.
Once the breaker is off for several hours (the breaking point seems to be around 4 hours), turning the breaker back on will not turn on the air handler automatically and the unit will function properly as controlled by the thermostat...for several hours, until it again reaches the point where the compressor and air handler do not come on concurrently.
If both are running properly and I shut off the thermostat, everything will shut down properly. However, even with the thermostat in the off position, the air handler will kick on indefinitely at some point on its own accord, and again cannot be turned off unless hitting the breaker. If this occurs, the compressor unit will not come on, ever, unless the breaker is off for several hours.
This has been occurring since we have had the house. Last night I noticed that the a/c was still functioning properly before I went to sleep (unusual). I shut down the thermostat and everything turned off. I left the breaker on. This morning I awoke to the air handler running but no compressor. I turned off the breaker. Approximately 3 hours later, when we went to turn on the a/c, the compressor would not come on, air handler was stuck on. The thermostat was showing a "flashing snowflake," which apparently indicates a fail-safe overheating measure to keep the compressor from kicking on and off too quickly and overheating, but the compressor had not been on at all.
After having the breaker off a couple more hours, it is back to normal. Compressor and air handler cycling as usual. Tonight will be the same story again.
I have tried reprogramming and resetting the temp on the thermostat. Resetting the target temperature works fine, if the system is in "running properly mode," that is, the air handler is not running indefinitely. Once the handler goes rogue, all bets are off. No amount of programming on the thermostat will affect the air handler.
To me this seems rather odd as sometimes the air handler follows the thermostat, other times not so much. The compressor always turns off by the thermostat, but not on. I cannot rule out the possibility that the unit was wired by a previous owner and was done totally incorrectly, as was the case with the plumbing and electrical systems, but I do not know enough about hvac wiring to determine what type of fault this could be.