In this month’s troubleshooting problem we have a homeowner who has attempted to repair his own equipment, and he has replaced two components. He installed a new thermostat and found that the problem was not solved, then followed that part replacement with a new transformer, which also didn’t solve the problem. The original symptom of the split system sitting dead still exists.
When you arrive, you find this seven-year-old, 3-ton system, which employs a gas furnace and outdoor condensing unit, is in good condition, and (see the equipment wiring diagram) you confirm that 120 vac is applied to the air handler equipment connections at L1 and L2.