faulty mains charging

Alasdairmor

Up until yesterday I have connected my autocruise vista motorhome successfully to the mains every 2 weeks during the winter.  I run a small heater  and also charge the two batteries.

Last night after hooking up I put on the charging supply switch, there was a small flash and the small micro switch tripped in the PMS5 panel..   The main one did not.   I disconnected the supply cable and tried the charging switch but nothing as expected
happened.

I ran the engine for about 15 minutes, switched off and both batteries tested higher than before showing that normal charging was OK.

Anyone able to help me, Alasdair?