Trailer lights

disco 300 tdi 1996, opps forgot that bit

We had a similar problem, check the Disco brake light bulbs ...

One had a loose filament which occasionally connected and occasionally didn't .. When towing the indicators and dash tell-tale would work until the brake applied then the indicators would work but not the tell-tale or vice-versa ... took ages to track it down 'cos both Disco brakelights mostly worked when stood!

Didn't find it until I'd replaced the whole towing wiring and plug, the caravan towing wiring and plug/sockets, and half the whole 12v electrics on the caravan!

Mind .. it needed it ... ;)

You have to think about volt drops across bad connection and the bulbs and work out where the volts are going when they aren't across the bulbs. Remember the volt drops will change with load, are the indicators fully bright or "just working"?. Does the brake light work and it's just that the indicator stops, how about hazards?

Most vehical lighting wiring does my head in as well, all to save a few pence on a wire here or there.

sketch out the system, including all the connectors and earths.

Then "diss" one earth, and you'll easily figure what and why.

As a test, try a seperate earth wire, from the trailer to the tug.

Dave B.