Habitation Electrics

Possibly the isolating relay and / or its contacts are defective. When the ignition is turned on the relay operates in order to isolate the 12 volt system in the van (to prevent you driving with the water pump running for example). If this relay has a problem, that would explain your fault. Sorry, but I do not know where it is located in your Trident, but usually it will be either in the engine compartment, or near to the habitation battery.

Keith Ratcliffe wrote:Thanks for this - I tracked down the relay - there are three and the one that does the job you indicate is working fine and delivering 12V to the habitation system. The fuse is OK as well. Wonder if the Zig panel itself is at fault?
Note: I found another post about these relays in a Topaz of similar age and mine are laid out differently. It seems they all have their little quirks.

If you have 12 volt present and the lights are not working, then it does point to the control unit. On our old Duetto there was a 'Plug-In System' control unit mounted above the sink unit and this had the switches for lights, pump etc. It also housed some fuses under a plastic cover. It would be worth having a look at your system for anything similar, a loose fuse could cause your problem. Just a thought.