Troubleshooting the E-20 (A-B) Pressure Switch Stuck Closed/Open Error Code

Overview

E-20 A - Pressure Switch Closed

The air pressure switch is detected in the closed position before the combustion fan starts. The ignition sequence cannot begin because the control system expects the pressure switch to be open when the fryer is turned on to start the heat sequence.

Common Causes:

• Pressure switch contacts stuck closed.

• Incorrect GMU high-limit jumper configuration.

• Failed pressure switch.

• Blower continues to run when heat is turned off.

E-20 B - Pressure Switch Open

The air pressure switch did not close within 60 seconds after the combustion fan started. This indicates that the combustion fan is not creating enough airflow or the pressure switch is not responding correctly.

Common Causes:

• Combustion fan not operating or is faulty.

• Faulty blower control board.

• Blocked, leaking, or disconnected sensing tube.

• Faulty pressure switch.

• Blocked flue or vent system.

Call Avoidance Steps

The following checks may be performed remotely or by the customer before dispatching a technician:

For E-20 A - Pressure Switch Closed

1. Power cycle the fryer.

2. If the fault immediately returns after restart, schedule service.

For E-20 B - Pressure Switch Open

1. Power cycle the fryer.

2. Listen or verify combustion fan is blowing air from rear flue vent.

3. Verify rear flue vent and is not blocked.

4. If the combustion fan does not start or the fault continues, schedule service.

Field Troubleshooting

Accessing Service Mode

1. Enter the Settings menu on the control and select Service.

2. Enter code 1122.

3. Select Heat System.

4. Select Combustion Fan to turn the fan on and off manually.

5. If it is a split vat, test the output voltage to the blower control board from each GMU to verify you are receiving the 24 VDC properly.

Troubleshooting E-20 A - Pressure Switch Closed

Checking Pressure Switch Status with Unit at Rest

1. Disconnect power and test switch continuity.

2. If the switch is open as expected, see Verify GMU high-limit jumper configuration.

3. If the switch remains closed with no fan operation, replace the pressure switch.

Verifying GMU High-Limit Jumper Configuration

• Check that all high-limit jumpers are installed correctly according to the unit configuration.

  • The High Limit probes are specific to full vat or split vat configurations. If the jumper is in the wrong place, it will not start the ignition sequence due to seeing a fault in the safety check. If the jumpers are incorrect, replace high-limit probe and test.

Checking Wiring

1. Verify there are no shorts in the wiring.

2. Replace wiring as needed.

Troubleshooting E-20 B - Pressure Switch Open

Verifying Combustion Fan Operation

1. Start the unit and observe the combustion fan. If the fan is not running, troubleshoot the blower control board and supply voltage to the fan.

   • Verify if the blower control board is receiving 24 VDC input from the GMU on the P1 or P2 connections, depending on configuration of vat. Check wiring and replace GMU if no voltage is present is present on either connection.

     IMPORTANT: If this is a split vat, the voltage will only show up on the side being tested.

   • Verify the blower control board is sending out line voltage to the blower. If line voltage is not being sent to blower, replace blower control board.

2. If the fan is running and is receiving full line voltage, turn power off and clean blower wheel. If issue persists, replace blower.

Inspecting Pressure Switch Tube

• If moisture is found, continue turning the heat system on and allowing the blower to help dry out the tube and switch. This may require a few minutes of running the fan. If moisture is the problem, once dry the system should go into its normal heating operation automatically.

  • Check for leaks, cracks, loose connections, moisture, or disconnection of the tube from the flue to the pressure switch. Replace tube as needed.

Checking for Venting or Flue Restrictions

• Inspect the flue and tube nozzle for restrictions or blockages. If a blockage is found, remove the obstruction and retest.

Testing Pressure Switch Operation

1. Measure switch continuity while the combustion fan is operating.

2. If the switch does not close under proper fan pressure, if a manometer is available, verify the pressure generated by the combustion fan is at least .40wc, otherwise replace the pressure switch.

Retesting Unit Operation

• If E-20 B error returns, continue diagnosis of airflow, wiring, and control components.

Other Troubleshooting

E-20 A - Pressure Switch Closed

Rare causes may include:

• Water accumulation inside the sensing tube causing false pressure readings.

• Wiring short causing the control board to see a closed switch.

Verify wiring integrity and confirm pressure switch state directly with a meter before replacing electronic components.

E-20 B - Pressure Switch Open

Rare causes may include:

• Intermittent combustion fan performance due to worn bearings or voltage issues.

• Partial vent restrictions that only occur under certain operating conditions.

• Condensate accumulation affecting airflow or pressure sensing.