Lucca M58: Resetting and Testing the Safety Switches

If your M58 has stopped heating, but both heating indicator lights and PID remain on, here's a likely fix for that scenario.

• Philips head screwdriver

1. Turn off the machine, unplug it from the wall and allow it to fully cool if hot

2. Remove the panels from your machine.

3. Locate both safety switches and depress the center button; you should feel a slight "click".

4. The safety switches on newer model M58s look a bit different, but function the same way. Here's where to find them:

Brew Boiler


Steam Boiler

Testing the Safety Switches
If the safety switches have not been tripped, but the machine still fails to heat, it's a good idea to test the safety switches to be sure they're working correctly. If the switch is not tripped, electricity should be able to flow freely from one side of the switch to the other. We can test this with a multimeter. This test will be done while the machine is unplugged and cool.

1. Set your multimeter to read resistance (Ω) in the 20Ω range.
2. Backprobe both of the connectors on each safety switch as shown below.
(Make sure that both probes are securely touching the metal connector underneath the white plastic covers.)


3. A working safety switch will read a low resistance value when not tripped, usually <1.0Ω. This tells us that electricity is able to pass through.

4. A faulty safety switch will prevent electricity from passing through, even when not tripped. This can be verified by a very high resistance value (+20Ω) or no continuity at all (OL).