How to Fix / Troubleshooting

Safety first: Isolate power before inspecting internal wiring.

Check flow and filtration: Ensure strong, steady flow through the heater by cleaning filters and verifying pump performance.
Inspect safety circuits: Gently tug each wire on high limit thermostats, flow switches, and pressure switches to ensure firm connections.
Look for heat damage: Examine connectors and terminals for discoloration or melting.
Monitor operation: After reassembly, run the heater and observe whether shutdown coincides with pump speed changes or other equipment switching.

Intermittent faults can be complex; if the issue persists, a technician should test each safety device and the control PCB.

Heater starts but shuts down after a few minutes without showing an error code.

Possible Causes