Furnace blower runs but burners do not light; cool air from vents.
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 warning: If safety switches are open, there may be an overheating or flame rollout condition. Do not bypass safety devices.
Homeowner checks:
- 1. Power cycle furnace: Turn power off for 30 seconds, then back on. Call for heat and observe the sequence. If the blower starts without inducer or ignition, a safety or control fault is likely.
- 2. Inspect rollout and limit switches: With power off, check for manual-reset rollout switches that may have tripped. Only reset once after confirming there is no visible damage or blockage.
- 3. Check ignitor: Look through the sight glass during a call for heat. If the ignitor never glows, it may be failed and require replacement.
When to call a professional: Diagnosis of gas valve and control board issues should be done by an HVAC technician familiar with Philco furnaces.