uptonogood Posted April 6, 2012 Share Posted April 6, 2012 i have a 2001autotrail scout both top lights and the lowerlight on the drivers side do not work,checked the fuses they are ok and the brake light still works, help any ideas would be much appreciated. Thanks Link to comment Share on other sites More sharing options...
thebishbus Posted April 6, 2012 Share Posted April 6, 2012 Hi. We had a similar problem on our previous Burstner M/H. The top lights had a 12 volt + supply via a fuse, but the negative connection was to the aluminium skin, and then to the chassis. The problem was a high resistance connection between the aluminium skin and the chassis. Brian B. Link to comment Share on other sites More sharing options...
Keithl Posted April 6, 2012 Share Posted April 6, 2012 Hi Bob and welcome to the forum. First things first, are you sure that there is a fault and that quite simply the 3 bulbs have not all failed? Then, if not, do you have a multimeter or 12v test lamp? If so can you first test that the meter or lamp ACTUALLY works between say the brake light feed and it's earth, then test for power at the feed to the non-working side light and the SAME earth point. I will hazard a guess that there will be no power at the side light feed and follow on accordingly. So next test for power at BOTH sides of the fuse with it in place, most fuses have small openings in the top to allow for connecting a test probe. If you have power here then you need to start following the wiring from the fuse rearwards or light forwards. Our 2004 AT has a junction box mounted on the LH chassis rear extension just behind the rear wheel, does yours have anything similar? Try the above and let us know how you get on. Keith. Link to comment Share on other sites More sharing options...
uptonogood Posted April 6, 2012 Author Share Posted April 6, 2012 Thanks for your replys this motorhomein stuff is all new to use so feeling our way around at the moment. Will go with you advice and see what happens thanks Link to comment Share on other sites More sharing options...
uptonogood Posted April 7, 2012 Author Share Posted April 7, 2012 Found the fault on the light problem the wire to the upper and lower lights had broken, so sorted that out and now works .Heres another one for you,when the main lights are on and you put your foot on the brake only the top strip brake lights work,if i turn off the main lights and press the brake all three brake lights work. Now i know why im a carpenter not a sparks does my head in, any idears thanks Bob Link to comment Share on other sites More sharing options...
Keithl Posted April 7, 2012 Share Posted April 7, 2012 Bpb, Simple, you've lost the earth to one or other (or maybe both) of the main light units and when sidelights are off the brake lights are earthing through the sidelight circuit. When you turn the sidelights on you have 12v at both sides of the brake lights so they do not work. What happens to the sidelights if you press the brake pedal when the sidelights are on? Keith. Link to comment Share on other sites More sharing options...
uptonogood Posted April 7, 2012 Author Share Posted April 7, 2012 Keith, here we go the side lights stay on only the strip light brake works there are two filiments on the side light bulb which i assume are brake +normal lights ps where is the earth cable? Link to comment Share on other sites More sharing options...
Keithl Posted April 7, 2012 Share Posted April 7, 2012 Are your rear lights the same as ours, Hella CaralunaMk2 like this Link ? If so all the bulbs are mounted in a metal strip across the back of the light unit and there will be one wire connected onto this metal strip. This will be the earth so try following it back and see where it goes or test it is actually earthed by using your multimeter or test lamp between this earth and a known live. Edit, make sure you disconnect the earth wire before testing it to prevent false readings through the bulbs and other circuits. Keith. Link to comment Share on other sites More sharing options...
uptonogood Posted April 7, 2012 Author Share Posted April 7, 2012 Spot on same lights and there is an earth on the metal back plate on both units, to follow the earth cable is tricky as all wraped up together but will try tomorrow what would testing between the earth and a live cable tell me? Link to comment Share on other sites More sharing options...
Keithl Posted April 7, 2012 Share Posted April 7, 2012 That the earth really is an earth and that lights are not feeding back through each other. Another way to prove the point would be to run a temporary wire from a known earth point somewhere else to the metal plate and see if the lights work correctly. Keith. Link to comment Share on other sites More sharing options...
uptonogood Posted April 7, 2012 Author Share Posted April 7, 2012 ok thanks will try this tomorrow fingers crossed Link to comment Share on other sites More sharing options...
uptonogood Posted April 8, 2012 Author Share Posted April 8, 2012 Did as was suggested put a temp cable from the earth point on the light to the metal chassis of the van,this made on differance where would a known earth point be? Link to comment Share on other sites More sharing options...
Rayjsj Posted April 8, 2012 Share Posted April 8, 2012 The Motorhome Chassis, or run a longer wire back to the Battery negative terminal, you are only testing that 'Bad Earthing' IS the problem. Ray (just being a nosey parker !). Link to comment Share on other sites More sharing options...
uptonogood Posted April 8, 2012 Author Share Posted April 8, 2012 Thanks for your help so far but its not over yet!!!. So lights are as decribed brake lights not working when lights are on,i put a cable on the earth on the light and on to the chassis still lights where the same, so hit a bit of a wall. Help Link to comment Share on other sites More sharing options...
Keithl Posted April 8, 2012 Share Posted April 8, 2012 Hi again Bob, I'm struggling to get my head around your problem at the moment as the problem points to a classic earth fault. Do you have a Voltmeter? If not can you beg, steal or borrow one? You only need a cheap one, max £10 will do fine, say something like this one from Maplin... Link. 1. With all the wires connected to the light unit and the sidelights on what is the voltage between the sidelight feed wire and the earth? 2. Now press the brake pedal and does the reading change? 3. Next, turn the sideleights off and get someone to press the brake pedal, measure the voltage between the brake light feed wire and earth? 4. Now turn the sidelights on still with the brake pedal pressed? If any of these readings alter from 1 to 2, or 3 to 4, repeat and substitute your chassis earth for the light unit earth. Report back and I'll analyses the results. PS What area of the country are you from? Keith. Link to comment Share on other sites More sharing options...
uptonogood Posted April 8, 2012 Author Share Posted April 8, 2012 Ok keith have got a voltmeter so will try as you suggested, i live in wiltshire thanks again Link to comment Share on other sites More sharing options...
uptonogood Posted April 9, 2012 Author Share Posted April 9, 2012 To all veiwers of this problem simplicity is the answer,after swopping the bulbs over to check that they worked i must have put them in the wrong way round.There are two elements in these bulbs one for lights one for brakes get them round the wrong way and the brake lights dont work with the lights on.Thanks to keith for your help and patience with this matter,i hope this will help others in the future. One happy motorhome owner. Ps Dont let me change your bulbs for you. Link to comment Share on other sites More sharing options...
Keithl Posted April 9, 2012 Share Posted April 9, 2012 Hi Bob, So glad to hear you're sorted and that my offerings where of help. It's always the simplest things which are hardest to find! All the best (until next time :D ). Keith. Link to comment Share on other sites More sharing options...
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