MSPA spa shows E3 and will not heat; pump may run briefly then stop.

Safety first: Unplug the spa before reaching into the water or removing fittings.

• Verify water level: Fill the spa to the level indicated in the MSPA manual (usually between MIN and MAX marks). Underfilling is a common cause of E3.
• Bleed air from system: After filling, gently rock the spa walls to release trapped air bubbles from the pump and heater. On some MSPA models, briefly run the bubble function to help purge air, then try the heater again.
• Clean or replace filter: Remove the MSPA filter cartridge from the housing. Rinse thoroughly from inside out with a garden hose. If the pleats are collapsed, oily, or discolored, replace the MSPA filter cartridge.
• Check suction and return: Inspect the suction cover and outlet jet for debris, leaves, or toys. Remove any obstructions. Ensure the filter housing is correctly installed and not drawing air.
• Restart system: Reconnect power, run filtration for several minutes, then enable heating. If E3 returns immediately, the flow sensor or pressure switch may be faulty and require replacement.