Pentair Max-E-Therm ERR AGS Error
The ERR AGS error on a Pentair Max-E-Therm indicates the automatic gas shutoff has activated. Water temperature after the second pass through the heat exchanger exceeds 140F.
This is a serious safety fault. Front panel buttons are disabled. Cycle power to reset.
What Causes ERR AGS?
The automatic gas shutoff (AGS) is a secondary safety system that triggers when water gets dangerously hot, beyond what the high limit switch (HLS) should have prevented.
Common Causes
- Severely restricted water flow: Much worse than HLS conditions
- High limit switch failed: Didn't stop heater first
- Severe scale buildup: In heat exchanger
- Gas pressure too high: Excessive heat output
- Temperature sensor issue: False reading
- Heater grossly oversized: For the application
This is a Serious Fault
WARNING: ERR AGS means water reached dangerous temperatures. Do not simply reset and continue operating without investigation.
Troubleshooting Steps
Step 1: Cycle Power to Reset
- Turn off power to heater
- Wait 30 seconds
- Turn power back on
- Do NOT attempt to heat immediately
Step 2: Investigate Cause Before Restarting
Check Water Flow
- Verify pump is running
- Check filter pressure
- Ensure valves are properly positioned
- Inspect for blockages
Check High Limit Switch
ERR AGS often means HLS should have triggered first:
- Test high limit switch operation
- It may be failed or bypassed
Inspect Heat Exchanger
- Look for signs of scale
- Professional inspection may be needed
- Descaling service may be required
Step 3: Test Before Normal Operation
- Verify adequate water flow
- Start heater and monitor closely
- Watch for HLS to trigger first if problem persists
- If AGS triggers again, do not continue using heater
When to Call for Service
Call a qualified technician if:
- ERR AGS keeps recurring
- High limit switch needs testing/replacement
- Heat exchanger inspection needed
- Gas pressure adjustment required
- Cause cannot be determined
Prevention
- Maintain proper water flow
- Keep water chemistry balanced
- Have heater serviced annually
- Don't ignore HLS errors