Thermostat shows normal operation but HVAC system does not turn on in any mode (heat, cool, or fan).

Safety first: Turn off power to the furnace/air handler before accessing wiring.

• Verify mode and setpoint: Ensure the thermostat is in the correct mode (HEAT/COOL) and the setpoint is above/below room temperature as appropriate.
• Check wiring at thermostat: Confirm R, C, Y, W, and G wires are properly connected and not corroded.
• Check wiring at control board: At the Payne furnace/air handler, verify that the same wires are secure on the control board terminals.
• Test manual jumper (advanced): With power off, place a jumper between R and G on the control board. Restore power; if the blower runs, the board is responding. Similarly test R to Y (cool) and R to W (heat). If equipment responds to jumpers but not to thermostat, the thermostat or cable is faulty.
• Replace cable or thermostat: If continuity tests show an open conductor, replace the thermostat cable. If the cable is good but no response from thermostat calls, replace the thermostat.
• Replace control board: If the equipment does not respond even to R‑X jumpers, the Payne control board or downstream components are faulty and should be serviced by a technician.