Doug Hall Posted June 18 Share Posted June 18 I have two electrical problems with my 2008 Roadsport SV: The high beam on the nearside has stopped working - without the bulb there is a 12V supply, once the bulb is connected there is no supply so the high beam of the bulb doesn't work, which is a mystery - any ideas? The reversing light has stopped working - the bulb is fine so I suspect the switch or the wiring - the switch must be on the gearbox somewhere and inaccessible wherever it is - before I start searching for it can anybody offer any guidance on its location? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 18 Member Share Posted June 18 Do you have the appropriate wiring diagrams? Please let me know if you need any. And do you have a multimeter and know how how to use the voltage range and the continuity testing? Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 18 Member Share Posted June 18 14 minutes ago, Doug Hall said: The reversing light has stopped working - the bulb is fine so I suspect the switch or the wiring - the switch must be on the gearbox somewhere and inaccessible wherever it is - before I start searching for it can anybody offer any guidance on its location? Yes, rear underside of the gearbox. It might have either one or two terminals. NB the circuit works by switching the earth side at the switch in the gearbox. So you need to check whether the switch is connected and whether the switch connects internally when reverse is selected: single terminal to earth, or two terminals to each other. Lamp is incandescent, not LED? The feed to the lamp is not switched, and should be LIVE whenever the ignition or sidelights are ON (I can't remember which). So check that, and once you know that it's live then connect a temporary earth to the lamp unit as a test. Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 18 Member Share Posted June 18 9 minutes ago, Doug Hall said: The high beam on the nearside has stopped working - without the bulb there is a 12V supply, once the bulb is connected there is no supply so the high beam of the bulb doesn't work, which is a mystery - any ideas? All incandescent lamps, not LED? Do you mean that the 12V at the live connector on the bulb holder drops to nothing? Does the side light on the same side stop working when you do this? Does the high beam on the other side stop working when when you do this? I'd start by mocking up the circuit with the bulb out of the holder so that you know that the switches and feed and bulbs are OK. And then investigate what's happening to the live and earth sides at the holder when you insert the bulb. Jonathan Link to comment Share on other sites More sharing options...
Gridgway Posted June 18 Share Posted June 18 for the high beam, feels like an earth problem. When you test for the 12v where do you get the earth from? Have you checked the continuity from the 0v connection to the bulb back to the -ve terminal of the battery? Link to comment Share on other sites More sharing options...
Doug Hall Posted June 18 Author Share Posted June 18 Hi thanks for your advice Re the headlight: The bulb is incandescent I don't think it is an earth problem as the low beam on that bulb works fine, as does the side light on that side Without the bulb connected the multimeter shows 12v connected to the high beam and nil when the bulb is connected The other side is fine on the high and low beam and side light I've mocked it up without the bulb and get a 12v supply I'm assuming there isn't a relay for the headlight high beam? Re the reverse switch: I'll jack up the car and have a look! Link to comment Share on other sites More sharing options...
Gridgway Posted June 18 Share Posted June 18 Where are you taking the earth from for the test, especially when you say you get 0v when the bulb is connected? Link to comment Share on other sites More sharing options...
Doug Hall Posted June 18 Author Share Posted June 18 I'm taking the earth from the body of the headlight, which the low beam and side lights are also connected to which work Link to comment Share on other sites More sharing options...
Gridgway Posted June 18 Share Posted June 18 So then it can only be on the supply side (assuming you've tried swapping bulbs - no idea how that could be a thing, but worth trying if you've not done so). I'd be trying to test the resistance of the +12v side of the connector to the bulb to the +12v battery connection (battery disconnected clearly). Then I might try a fly lead from the +ve supply from the other main beam and vice versa if that makes sense? Link to comment Share on other sites More sharing options...
Doug Hall Posted June 18 Author Share Posted June 18 Yes that makes sense thanks and I'll give it a try Link to comment Share on other sites More sharing options...
raw Posted June 19 Share Posted June 19 Check the earth to the reverse light. The standard arrangement is never very good but if the bulb is working and you have 12v then check that the earth is not corroded. Headlight - have you tried the working bulb in the non-working side? Link to comment Share on other sites More sharing options...
Doug Hall Posted June 19 Author Share Posted June 19 Mystery solved - corrosion on the spade terminals on this connector which is zip tied to the chassis member next to the headlight. seems like it would be useful if that was waterproof! Many thanks for your help! Link to comment Share on other sites More sharing options...
Gridgway Posted June 19 Share Posted June 19 Good result. Presumably the corrosion problem was with the 12v supply? Link to comment Share on other sites More sharing options...
John Vine Posted June 19 Share Posted June 19 Thanks for the update. That connector looks non-standard. Normally it would be a 6-way sealed Econoseal. Are your headlights/wiring non-standard? JV Link to comment Share on other sites More sharing options...
Doug Hall Posted June 20 Author Share Posted June 20 Yes the corrosion was on the 12v supply That connector is what was supplied with the car when I built it from a kit - I'm replacing both sides with waterproof ones I've discovered that one of the terminals on the reverse light switch has been broken off - I reckon it happened when I had some work done on the gear box about 3 years ago but I hadn't noticed! The requirement for the reverse light to work to pass an MOT was only brought in for vehicles registered in 2009, the year after mine so it still passed. Thanks for all your help - I can sort out both problems now. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 20 Member Share Posted June 20 Well done. Jonathan Link to comment Share on other sites More sharing options...
John Vine Posted June 20 Share Posted June 20 38 minutes ago, Doug Hall said: I'm replacing both sides with waterproof ones Good idea! Thanks for the update. JV Link to comment Share on other sites More sharing options...
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