Pentair Max-E-Therm Troubleshooter

ERR IGN means Ignition Failure. The heater attempted to light three times and was unable to detect a flame. Common causes include a closed gas supply valve, insufficient gas pressure, a fouled or cracked igniter, or a dirty flame sensor. Start by verifying the gas supply is on and other gas appliances in your home are working. If the gas is fine, a technician will need to inspect the igniter, flame sensor, and gas valve.

ERR PS is the Pressure Switch error. The heater's pressure switch did not detect adequate water flow before attempting ignition. The most common causes are a dirty filter, a closed valve in the return line, or a pump that is not running at the required minimum flow rate. Clean the filter, open all valves, and verify the pump is running before calling a technician.

ERR HLS is the High Limit Switch error. This safety switch trips when it detects water temperature approaching an unsafe level near the heat exchanger, usually because of low flow through the heater. Check that the pump is providing adequate flow, the bypass valve is not diverting too much water away from the heater, and the filter is clean. If the switch trips repeatedly even with good flow, the heat exchanger may have scale buildup and needs professional inspection.

ERR AFS stands for Air Flow Switch. This error occurs when the blower vacuum switch does not detect negative pressure during the pre-purge cycle. Common causes include a blocked exhaust vent, debris in the air intake louvers, a cracked or disconnected vacuum tube between the blower and the AFS, or a failing blower motor. Check the vent termination for obstructions first, and listen for the blower motor running before ignition.

ERR SFS is the Stack Flue Sensor error. The flue temperature sensor (a thermistor located in the flue collector) has an open circuit, short circuit, or is reading out of range. Try power cycling the heater first. If the error returns immediately, the sensor connector may be corroded or the thermistor itself may have failed. A technician can test the sensor resistance (approximately 10k ohm at 77 degrees Fahrenheit) to confirm.

Short cycling — where the heater fires, runs briefly, then shuts off — is typically caused by insufficient water flow through the heat exchanger. Check that the filter is clean, the pump is running at adequate speed (especially with variable-speed pumps), and the bypass valve is not diverting too much water around the heater. Scale buildup inside the heat exchanger can also cause the temperature rise to be too high, tripping the high limit switch and shutting down the heater.

Yes. Select the "Homeowner" role and the wizard will show only the checks that are safe and practical for a non-professional to perform. Technician-level steps such as voltage measurements and gas pressure testing are hidden unless you switch to Technician mode. Always follow the safety warnings on screen, and consult a licensed pool service professional for any repair you are not comfortable performing.