Henny Penny E-20A Error Code

What does Henny Penny E-20A mean?

E-20A means the air pressure (vacuum) switch has signaled the control that it is closed — indicating air flow is present — before the draft fan has been commanded to run. The control checks the switch state during startup to confirm the fan is off before initiating the ignition sequence; if the switch reads closed at that initial check, the sequence aborts with E-20A. This points to a switch stuck in the closed position or a wiring short.

Symptoms

• Display shows E-20A and the gas ignition sequence does not start.
• Draft fan may not be running at the time the error appears.
• Error occurs consistently at the beginning of every heat call.
• Pressing the Timer button to retry ignition does not clear the error.

Common causes

• Air pressure (vacuum) switch contacts stuck closed due to wear or debris.
• Wiring short between the switch signal wire and ground, simulating a closed switch.
• Vacuum hose to the switch kinked or blocked, holding residual pressure.
• Fan running continuously when it should be off, keeping the switch closed.
• Defective control board unable to read the switch state correctly.

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Diagnostic steps

1. Retry ignition via Timer button

   Press the Timer button to re-attempt the ignition sequence. If the error clears on retry, it was a transient glitch; monitor for recurrence.

2. Verify the draft fan is not running at startup

   Listen and visually confirm the draft fan is not spinning before the heat call begins. A fan running continuously when it should be off will hold the air switch closed.

3. Inspect the vacuum hose

   Locate the small rubber hose connecting the air pressure switch to the draft fan housing. Check for kinks, cracks, or blockage that could trap pressure and hold the switch closed.

4. Test air pressure switch continuity

   Disconnect power and unplug the air pressure switch connector. Measure continuity across the switch terminals; a reading of closed with the fan off confirms the switch is stuck and requires replacement.

5. Inspect wiring for shorts

   Check the air switch wiring harness for chafed insulation or wires contacting the chassis. A wire-to-ground short mimics a closed switch and must be repaired before replacing the switch.

When to call a professional

If the air switch is replaced and E-20A persists, the control board may be misreading the switch input. A licensed technician must test the board's input circuit and gas valve wiring with a multimeter. Gas ignition system work also requires verifying proper combustion after any component replacement.