Question was because red light was coming on after fitting new 3 stage charger. Seems redlight is definately polarity and black button is RDC test. After much discussion with manufactures, etc.. the conclusion was it should not happen. On that basis I checked all wiring. Could not see any obvious issues. Tinned any wires that were bare. Vacuumed out cabinet. Reconnected, rerouted and tidied wiring. Problem has gone away. Always frustrating not to find an obvious solution. Will be keeping an eye. Thanks for everyone's help. I have drawn up the 240v circuit if anyone ever needs a copy.