Heater display shows E03 and the unit will not fire

Safety First: Turn off power to the heater and pump before working on the plumbing system.

• Verify pump operation: Ensure the pool pump is running and fully primed. Check for air in the pump basket and correct any suction leaks.
• Clean filtration system: Backwash or clean the pool filter. Empty the pump and skimmer baskets. A dirty filter is a common cause of low flow.
• Check valves: Confirm that all valves leading to and from the heater are fully open and that bypass valves are correctly positioned per Rheem installation guidelines.
• Inspect pressure switch: Locate the water pressure switch on the inlet manifold. Check wiring connections. With power off, remove the switch and inspect for debris in the port. If the switch does not close when there is good flow (test with a multimeter), replace it with a Rheem-approved water pressure switch.