NCM-300 SUPPLY AIR SENSOR faulty?

[marcot1]

Is it possible for the SUPPLY AIR SENSOR in a NCM-300 to become faulty or fouled producing incorrect temperature readings? I've moved into a 2 story house that had an already installed NCM-300 (Gas Forced air heat/ AC), I replaced both thermostats with Nest 3rd gen units last December. Now that warmer weather has come I've noticed that the outside AC unit cycles more then I would expect when the nest is still calling for AC (it does not matter which thermostat). I started looking into the NCM-300 and noticed that the SUPPLY AIR SENSOR LED is what is cutting the outside unit off and back on.

Thinking back to this winter the heat also cut on and off more frequently then I would have thought.

Is there any way to test the sensor (volt meter or other means) to determine if it is working? I don't want to ignore a potential issue with the main AC system but I can't imagine that it could freeze the coils after running for only 10-15 minutes. The settings on the NCM-300 are currently set to 45 degrees on the cool side and 155 on the hot side.

Thanks for any assistance.

[Paul Z.]

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