Water heater does not turn on at all; no lights or display on Marey tankless unit.

Safety first: Before opening the unit, turn OFF the breaker and verify no voltage is present.

Steps:

• Check house power: Verify the dedicated breaker for the Marey heater is ON and not tripped. Reset if necessary.
• Inspect power connections: Remove the front cover and check the power terminal block. Tighten any loose screws and ensure wires are correctly landed (L1, L2, N, ground as applicable).
• Internal fuse: If your model has an internal fuse, check and replace it with the exact same rating if blown.
• Test outlet (for plug-in models): Plug another device into the outlet to confirm it has power.

When to call a technician: If power is present at the terminals but the unit remains dead, the control board is likely faulty and should be replaced by a professional.