I can’t tell clearly from the photo as I can’t see what’s written against the connections on the board but it looks OK. Of course they are only the control voltage wires for the SSRs Your measurements are more useful as it indicates no current draw for the steam boiler. I think the small reading is because the wire has become live.
Logically it must be:
- Failed heating element
- tripped safety stat
- bad connection
The next thing to do is disconnect the heating element connectors from the steam boiler, run the test again and see if the readings are the same. Also to check for voltage at the steam boiler heating element connectors (which you might find easier to do with probes, before disconnecting them?
Be very careful, as even with the pathetic voltages used in the States, it can still kill.
