LED status light is on solid with no flashes; furnace does not run.

Safety first: Turn off power before checking wiring or fuses.

Step-by-step checks:

• 1. Confirm thermostat call: Set thermostat to HEAT and raise the setpoint. Listen for a click at the thermostat. If it does not click or display a call for heat, replace thermostat batteries or the thermostat itself.
• 2. Inspect low-voltage fuse: On many Philco control boards, a 3–5A automotive-style blade fuse protects the 24V circuit. With power off, remove and visually inspect the fuse. Replace with the same rating if blown.
• 3. Check thermostat cable: Inspect the cable from thermostat to furnace for damage (staples through wire, rodent damage). Repair or replace as needed.

When to call a professional: If the fuse continues to blow or there is no 24V output from the transformer, an HVAC technician should locate the short and test the transformer and control board.