Furnace does not respond to thermostat; LED status light flashes ten times repeatedly.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power before touching low-voltage wiring to avoid shorting the control board.
Step-by-step checks:
- 1. Verify thermostat settings: Ensure the thermostat is set to HEAT and the setpoint is above room temperature. Replace batteries if applicable.
- 2. Inspect thermostat wiring at furnace: Remove the blower door to access the control board. Check that R, W, G, and C wires are firmly attached and not shorted together. Look for bare copper touching the furnace chassis.
- 3. Test furnace with jumper (only if comfortable): With power off, temporarily connect a short jumper wire between R and W on the control board. Restore power. If the furnace starts normally, the thermostat or thermostat cable is likely faulty.
- 4. Remove jumper and restore normal wiring: Do not leave the jumper installed after testing.
When to call a professional: If the furnace will not respond even with an R-W jumper, the Philco control board may have failed and should be tested and replaced by a technician.