John Wood power vent water heater shows E016 and the blower runs continuously even when there is no hot water demand

Safety: Disconnect power before inspecting the control board and wiring.

• 1. Power cycle: Turn off power at the breaker for 5 minutes, then restore. If the blower starts immediately with no call for heat, suspect a stuck relay or wiring fault.
• 2. Wiring inspection: Check the blower power wires for shorts to line voltage that bypass the control board.
• 3. Listen for relay click: With the cover off (and using caution around live parts), listen for the blower relay clicking on and off when there is a call for heat. If the blower stays on regardless, the relay may be welded closed.
• 4. Replace control board: If the relay is stuck or the board is providing constant output, replace the main control board with the correct John Wood part.