Upon my diagnostic on a 1989 Lennox air handler heatpump, I discovered that the transformer tripping reset has been going off. Seated investigating all low-voltage wires coming into terminal blocks and thermostat and found that all wiring was correct. I then made my way outside to the condensing unit and found that the wire fished from the inside of the wall has been chewed up by a Rodent. Paired low-voltage wiring in the further inspection found no refrigerant pressures were adequate although did contain our 22 Freon which was been January 1, 2020 and found that fancy terminal capacitor was becoming weak. System make screens Mollo voltage short if rodent problem is not addressed. low-voltage wiring should’ve been run in in conduit as well.