When we went to Cheddar last December I noticed at the pre-flight checking stage that the caravan fog light was not working. I'd had trouble with this a few years ago and cured it by simply cleaning the bulb and terminals which were badly corroded but this time my simple remedy did not effect a cure.

On our return, I managed to track down an exact replacement 'Jotol' unit which I confidently mounted and connected only to be disappointed when this light with its new bulb and shiny chrome terminals didn't work either.

'Looks like a bad earth' I thought. 'All I have to do is find where the light earths to the chassis and clean or if necessary renew the earth wire to establish a good connection.' The only problem as I later discovered is that the lights are earthed not to the caravan chassis but back to the car via the 13-pin connector.

The first thing to check was whether I was getting power and earth from the car socket and here I am indebted to Ambrow Trailers of Christchurch, Dorset who connected up their test rig and declared the car electrics to be working perfectly and for which they kindly declined to take payment.

So, this morning I have been crawling in and out from under the van testing continuity between the terminals in the large, white plastic box, the pins on the 13-pin plug and the power and earth supplies to the fog light. After a great deal of faffing about and a fair amount of swearing I managed to determine that everything checks out fine.

Bugger! Where do I go from here?

Well, I started to write that a couple of hours ago and thought that before I posted it I really should hook the van to the car and do some more tests. To my surprise and delight, the fog light is now working as it should but as I didn't actually do anything other than trace and waggle a few wires about, I don't know what I did to cure it. Perhaps the clue is in the waggling of the wires? Maybe it was just a dirty connection all along?

Anyway, whatever the explanation, that's another job crossed off the to do list so I'm now a happy bunny.

Simple explanation. It's the Tale of Waggling the Fog
Randa