Heil LED Blink Codes | HVAC IQ Pro

Q: What does 1 flash mean on a Heil furnace?

Normal Operation. System is powered and in standby with no stored faults.

Q: What does 2 flashes mean on a Heil furnace?

System Lockout. Furnace locked out after maximum retries.

Q: What does 3 flashes mean on a Heil furnace?

Pressure Switch Error. Pressure switch stuck open or failed to close.

Q: What does 4 flashes mean on a Heil furnace?

Open Limit Circuit. High limit or rollout switch has opened.

1 Flash (slow) info

Normal Operation

System is powered and in standby with no stored faults.

Diagnostic Steps

No action needed

2 Flashes (slow) critical

System Lockout

Furnace locked out after maximum retries.

Probable Causes

Ignition failure
Flame proving failure

Diagnostic Steps

Power cycle to reset
Clean flame sensor
Test igniter
Check gas supply

3 Flashes (slow) high

Pressure Switch Error

Pressure switch stuck open or failed to close.

Probable Causes

Blocked vent
Bad pressure switch
Inducer failure

Diagnostic Steps

Check flue pipes
Test pressure switch
Inspect inducer motor

4 Flashes (slow) high

Open Limit Circuit

High limit or rollout switch has opened.

Probable Causes

Dirty filter
Low airflow
Rollout trip

Diagnostic Steps

Replace filter
Check airflow
Inspect rollout switches

Standing at the board counting flashes?

LaunchMyHVAC is live — free diagnostic checklists that document the test, a Manual J load calculator, and Hank the HVAC AI assistant. No signup for the tools.

Open the free tools →

Real-time monitoring hardware is still in development — join the launch list.