Reverse Polarity light issue

[woodsieboy]

I changed battery yesterday as in other post and all seemed well, left the mains charger on overnight to ensure it charged. This morning the Reverse Polarity light is showing on all the time on the Sargeny PSU, but when I put my tester into 13 amp socket it shows all good. If I turn off the charger the Reverse Polarity light goes out, so my thinking is that I have a problem with the charger. Sargent website has helpful QA but no specific mention of the RP light staying on.Can't contact my AWS technician or Sargent until tomorrow, so charger is turned off, mains is on to fridge and solar panel is charging the battery, any thoughts please?