Complete reference for all Pentair MasterTemp and Max-E-Therm heater error codes. Search by code, symptom, or keyword to find causes and fixes fast.
The Pentair MasterTemp and Max-E-Therm are among the most widely installed residential and light commercial pool heaters in North America. The MasterTemp line spans 125,000 BTU to 400,000 BTU (MasterTemp 125 through MasterTemp 400), while the Max-E-Therm covers the same BTU range with higher energy efficiency ratings. Both product lines use the same control platform and share nearly identical error code nomenclature.
When a fault occurs, the MasterTemp or Max-E-Therm display shows a short alphanumeric code that identifies the system component or safety circuit involved. Some codes point to simple conditions a homeowner can address, while others indicate safety-critical faults that require a licensed technician. Understanding what each code means helps you communicate clearly with your service company and avoid unnecessary wait times.
During normal operation, the MasterTemp display shows the current water temperature and the set-point. When a fault is detected, the display shows the error code in place of (or alternating with) the temperature reading. Some faults are lockouts that require a power cycle to clear after the root cause is resolved. Others are advisory warnings that do not prevent operation but indicate a condition that should be investigated.
The heater also stores a fault history that a technician can access to see recent error events. This is useful for intermittent problems that do not trigger a code at the time of the service call.
While some error codes have owner-level fixes, the following situations always require a licensed pool service technician or gas professional:
ERR IGN means Ignition Failure. The heater attempted to ignite the burner three times but never detected a flame. The most common causes are a closed or low-pressure gas supply, a cracked or fouled igniter, an incorrect igniter-to-ground spark gap, or a failed gas valve. Start by verifying the gas supply valve is open and other gas appliances work normally. If gas is confirmed but the heater still shows ERR IGN, call a pool heater technician.
For most fault codes, turn off the heater at the on/off button, wait 30 seconds, and turn it back on. If the code persists, turn off the heater breaker at the electrical panel, wait 30 seconds, and restore power. For ERR HLS (High Limit Switch), there is a physical manual reset button inside the heater cabinet that must be pressed after the root cause (typically a flow problem) is resolved. Always address the underlying cause before resetting to prevent equipment damage.
ERR PS (Pressure Switch) trips before the heater even attempts ignition. It means the water pressure switch did not detect enough flow to safely operate the heater. ERR HLS (High Limit Switch) trips during or after a run cycle. It means water near the heat exchanger reached an unsafe temperature, usually because flow was too low or the heat exchanger is scaled. Both codes point to a water flow problem, but they occur at different points in the ignition sequence.
ERR AFS is the Air Flow Switch error. The blower vacuum switch did not detect adequate combustion air during the pre-purge cycle before ignition. Common causes are a blocked vent terminal, a weakening blower motor, or a cracked vacuum tube on the air flow switch. ERR AFS prevents ignition, so gas is never released, but it can indicate a venting problem that could become a carbon monoxide hazard over time. Have the venting system inspected if this code appears.
This guide covers the current Pentair MasterTemp and Max-E-Therm product lines (post-2010 control boards). Older Pentair heaters, including legacy MiniMax and early MasterTemp models, may use different error codes and display formats. Always refer to the specific owner's manual for your model, which is available on Pentair's website using your heater's model and serial number.
Both E05 and E06 refer to the Stack Flue Sensor (SFS), which monitors the temperature of exhaust gases leaving the heat exchanger. E05 means the sensor circuit is open (disconnected wire or failed sensor reading infinite resistance). E06 means the sensor circuit is shorted (sensor reading near-zero resistance, usually from water damage or a failed sensor element). In both cases the sensor or its wiring must be inspected and replaced by a technician.
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