Gridgway Posted May 19, 2012 Share Posted May 19, 2012 I'm tracking down some trailer light gremlins in my BJ trailer. I think I have found the problem in one of the little sidelights. However, I've found something odd. I took all the bulbs out so I could check the continuity of the wiring and for most connections it's fine. For the +ve to the sidlights I get about 70 odd ohms from the trailer plug. Is there likely to be a ballast resistor to reduce the brightness of the little sidelights? 70 ohms is about 1/6th amp (roughly) so 2w at 12 volts, so sounds plausible. It also explains the fault I had where the spade connector feed to one of the sidelights was touching the earth (in the light unit). If it had been a dead-short it would've blown a fuse. Does this make sense? Thanks Graham Link to comment Share on other sites More sharing options...
Ian B Posted May 19, 2012 Share Posted May 19, 2012 I guess it's possible, but I would have thought unlikely - the simplest way to achieve less light is a lower wattage lamp (but I have little experience of trailer lights!). I would be more suspect of a corroded connector somewhere. Sorry, not much help was it! Link to comment Share on other sites More sharing options...
Gridgway Posted May 19, 2012 Author Share Posted May 19, 2012 Yes I agree, just strange that is the same both sides and both sides work! Link to comment Share on other sites More sharing options...
Paul Deslandes Posted May 19, 2012 Share Posted May 19, 2012 very unlikely and its not like that on mine. I would suspect a dirty connection in the trailer plug or at the bulb holder end. If you had 70 ohms in series with the bulb you'd only have about 170mA flowing with a short circuit which a cold bulb will look like. They have a positive temperature coefficient so the resistance only climbs up to limit the current as it gets hot. Remember also that you've got the number plate and, maybe, the front side lights also drawing current through the same cables so you'll have a 10 or 15 Watt load each side. Actually, thinking about it, I'm wondering if a connection to one of the bulbs has gone open circuit and you're reading the resistance via one of the other bulbs and its chassis connection. It'll be obvious when you find it. Edited by - Paul Deslandes on 19 May 2012 17:28:54 Link to comment Share on other sites More sharing options...
Gridgway Posted May 19, 2012 Author Share Posted May 19, 2012 Good thoughts there Paul. I took all the bulbs out to measure resistance otherwise it's not possible at all! The BJ trailer does not use the chassis as earth. So there are connectors to split the earth and (where necessary feeds). I don't have a car today with electrics to connect the trailer up to to see if those lights work, but I'm pretty sure they do. Strange! Graham Link to comment Share on other sites More sharing options...
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