Boiler will not start; display is blank and no lights are on

Safety: Electrical work should be done with power off at the breaker. Use a non-contact voltage tester if available.

• Check breaker and switch: Verify the boiler circuit breaker is ON and the local service switch near the Dettson boiler is in the ON position.
• Inspect power cord and wiring: Look for damaged cables or loose connections at the boiler junction box.
• Internal fuse: Many Dettson controls have a small replaceable fuse. With power OFF, locate and visually inspect the fuse. Replace only with the same type and rating if blown.
• Professional diagnosis: If power is present at the boiler but the display remains dead, the control board or transformer may be faulty and should be replaced by a technician.