York 5 Flashes

What does York 5 Flashes mean?

Five flashes means a flame that was established during ignition was then lost: the flame signal dropped below 0.2 microamps five times within one heating cycle. After the fifth loss the gas valve relay opens following a five-second inducer post-purge and operation is inhibited. The control resets by cycling first-stage heat, cycling 24 VAC power, or after the 60-minute watchdog timer expires.

Symptoms

• Burners light but go out repeatedly during a heat call
• Furnace short-cycles before locking out
• ICB flashes a counted burst of 5 on the LED
• Inadequate or intermittent heat output

Common causes

• Weak or contaminated flame sensor (≈1/8" gap to the right burner)
• Marginal gas supply or low manifold pressure
• Poor grounding causing erratic flame signal
• Dirty burners or air in the gas lines
• Wind, water, or a heat-exchanger breach disturbing the flame

Diagnostic steps

1. 01

   Inspect the flame sensor

   Verify the flame sensor is intact and positioned with an approximate 1/8-inch gap to the right burner; clean a contaminated sensor.

2. 02

   Verify gas delivery

   Confirm the gas lines are purged of air, inlet pressure is correct, and the gas valve provides proper manifold pressure.

3. 03

   Check grounding

   Verify proper grounding and that the 24 VAC common and cabinet ground references are intact, since a weak ground destabilizes the flame signal.

4. 04

   Clean the burners

   Confirm the burners are clean and free of blockages that could interfere with steady combustion.

5. 05

   Seal the heat compartment

   Verify there is no wind, rain, or snow entering the compartment and no air leaks or heat-exchanger breaches disturbing the flame.

When to call a professional

Repeated flame loss points to a flame-sensing, gas-delivery, or combustion problem that usually needs a micro-amp meter and manometer to diagnose. If cleaning the sensor and confirming gas pressure do not stop the dropouts, call a licensed HVAC technician. Because flame instability can indicate a cracked heat exchanger or venting fault, a professional should inspect combustion and the heat exchanger before the furnace is returned to normal service.