Several months ago we heard a "clicking" or snapping (like a whip) noise emanating from the thermostat in our hallway when we would put the A/C or heat on. It was an old style thermostat (dial) so we called a repairman and he said we needed to replace it with a new one. We have since had a new Honeywell thermostat installed and continue to hear a snapping/clicking noise after it's been turned on. The noise isn't continuous... but it happens enough to make one alarmed and concerned. When the A/C repairman was asked about it, he has reassured us that the sound is "normal" since it's the noise created by "arcing" between the filter and thermostat. There's an electronic air filter in the hallway ceiling just above where the thermostat is on the wall. Can anyone assure me this "clicking" noise is "normal"? We are trying to sell our home and the noise has been a concern to those viewing the house. When the thermostat is "off" there is no noise created.

Thanks