Pentair ERR AGS: Automatic Gas Shutoff
ERR AGS is a hard overheat lockout: water temperature exceeded roughly 140°F on its second pass through the heat exchanger, and the front panel disabled itself.
high severityApplies to: Pentair MasterTemp and MiniMax NT residential gas pool/spa heaters
What it means
ERR AGS is one step past ERR HLS, not a repeat of it. Where the high-limit switch trips on the first sign of excess heat, automatic gas shutoff is the backup that fires if temperature climbs even further on a second pass through the heat exchanger, around 140°F. When it trips, the control board doesn't just stop the burner — it disables the front panel entirely, which is why a simple power-cycle sometimes won't clear it. That's deliberate: a heater that got hot enough to trigger a second-stage safety after a first switch already tripped usually has a real flow or scale problem underneath it, and the lockout exists so nobody just resets past it over and over.
Likely causes
Each of these describes a heater whose heat exchanger is producing more heat than the water passing through it can absorb and carry away.
- Severely restricted water flow combined with continued burner operation
- Heavily scaled heat exchanger
- A failed high-limit sensor circuit
What you can check yourself
There are exactly two things worth trying yourself before this becomes a service call.
- Turn the heater off, verify normal flow and let the system cool completely
- Power-cycle at the breaker to attempt to clear the lockout
This is a hard overheat safety lockout by design. If it doesn't clear with a power cycle after confirming flow, or it recurs, have a licensed technician inspect the heat exchanger and sensor circuit — don't keep resetting and restarting a heater that's overheating.
Sources
Related reading
- All Pentair error codes
- Pentair ERR HLS — high-limit switch open
- Pentair ERR PS — water pressure switch open
- Symptom: Heater Runs But Pool Isn't Getting Warmer