I second Joe's opinion. You may be able to do the HVAC guy's job by getting the model info from the air handler and beating up Google a little. There may be a known problem and a fix from the manufacturer. It is probably as simple as a noise filter kit.
I am guessing they use an antenna, not cable?
If it is cable/satellite, those guys may have something too.
It could be as simple as an unterminated TV cable somewhere.
