On the only day in three and a half years that I've needed my rear fog light and, to my shame, the first time I've actually checked it, the pre-flight check showed that it wasn't working. I didn't have time to investigate further so we had to set off in dense fog for the Channel Tunnel without a fog light.

As soon as I removed the cover this morning the reason for the failure was obvious; the contacts on the bulb and bulb holder were badly corroded. I removed the whole unit (only two screws hold it to the bodywork) and set to work with emery paper and a file until everything was gleaming bright again.

I checked that the bulb was OK with a bit of wire across the car battery and then put everything back together. What I did notice was that the plastic lens on the light doesn't have a rubber sealing gasket and that there was moisture in the lamp unit. This was obviously the cause of the corrosion over the past 13 years.

Fog lamp01.jpg - Bild entfernt (keine Rechte)

I then tested for continuity in the circuit by connecting my multimeter (set to resistance) across pins 2 and 3 on the caravan 13 pin socket and everything was OK. See this link for the pin numberings: 13 pin socket.

To be absolutely certain that all was well I then connected the electrics to the car and switched on. All was operating as it should. It's a fix!

The problem now was how to seal the unit so that water couldn't get in? My first thought was to strip the insulation off a piece of wire, split it lengthways and then fit it over the edge of the plastic with the joint at the bottom. When I mentioned this to Mrs Calder, however, she said without hesitation, "Why don't you use a rubber band?" and then produced one of exactly the right size from the kitchen drawer. She can either be a) frighteningly practical on occasions or b) a bit of a smartarse. In this case it was definitely an a but with a hint of b..

So, that's what I've done. Obviously, the rubber band will perish over time but it's such an easy thing to replace that it's not really an issue.

Fog lamp02.jpg - Bild entfernt (keine Rechte)

Before the bad winter weather starts, could I suggest that you check that your fog light is working and if necessary give the bulb and its contacts a good cleaning? The high intensity light from your fog light could give that vital second or two extra braking time for someone coming up behind you and help prevent a nasty accident.

Quote: Aaron Calder wrote in post #1

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...the contacts on the bulb and bulb holder were badly corroded. I removed the whole unit (only two screws hold it to the bodywork) and set to work with emery paper and a file until everything was gleaming bright again.

I checked that the bulb was OK with a bit of wire across the car battery and then put everything back together.

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Sound advice, Pete.

I'll fit a new bulb in a couple of days.

Quote: Steamdrivenandy wrote in post #2

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I recall a service on our '01 Troll a couple of years back when the mobile servicing guy checked the rear lights and the fog wasn't working. His first action was to thump the van with the flat of his hand near the offending lamp. As if by magic the lamp lit up. His only comment, a laconic 'that's what 20 years in caravan servicing teaches you'.

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Quote: Agger wrote in post #7

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I check ALL my lights before setting off, it's part of my responsi ility to other road users

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