Machine displays ALARM 5; brew boiler temperature rises uncontrollably or is reported as excessively high, and heating is disabled.

Safety first: Immediately switch OFF and unplug the machine if you suspect overheating. Do not touch the boiler or internal components until they have cooled.

Steps to address ALARM 5:

• Allow full cool-down: Wait until the machine and boilers are at room temperature before opening panels.
• Inspect the brew boiler SSR/contactor: Locate the solid-state relay or contactor that controls the brew boiler heating element. Check for signs of overheating (discoloration, melted plastic, burnt smell).
• Check if SSR is stuck closed: With the machine unplugged, disconnect one lead of the brew heating element. Use a multimeter to verify that the SSR output is open (no continuity) when the machine is off. If it shows continuity when it should be off, the SSR is stuck and must be replaced.
• Verify brew temperature probe: Inspect the probe wiring and connector. Test resistance at room temperature and compare to spec. A probe that reads too low can cause the controller to overheat the boiler.
• Inspect for scale: Heavy scale can cause hot spots and inaccurate sensing. If the machine is heavily scaled, plan a full descaling procedure or professional boiler service.
• Replace faulty components: Replace any failed SSR/contactor or brew temperature probe with La Marzocco-approved parts. Ensure all connections are tight and properly insulated.
• Persistent overheat alarms: If the hardware is sound but ALARM 5 recurs, the main control board’s regulation circuit may be defective. Contact an authorized technician.