RogerH Posted July 30, 2023 Report Share Posted July 30, 2023 (edited) Hi Folks, had an MOT yesterday and the man found that my sidelights were pulsing with the indicator lights. The side lights are LED. Had a quick check this morning and found that if I power the sidelights with a fly lead straight from the battery the pulsing stops. Could it be that the indicator wire (Green/White) is running along side the Red sidelight power wire and giving some sort of transformer effect. I know that Neon bulbs can suffer from this. Tomorrow - more investigation and a fix. Roger Edited July 30, 2023 by RogerH Typo Quote Link to post Share on other sites
RobH Posted July 30, 2023 Report Share Posted July 30, 2023 (edited) 56 minutes ago, RogerH said: Could it be that the indicator wire (Green/White) is running along side the Red sidelight power wire and giving some sort of transformer effect. Very unlikely - the current required is too high for that (neons only draw microamps). Are these 'dual-filament' LED bulbs or have you separate ones for indicator and sidelights? Some dual LED bulbs use a common set of elements driven either with high current or low current to give the separate brightness. In some bulbs It is possible for current to feed back from the high current side to the low current one. There may be enough leakage to power a small LED lamp on the sidelight circuit. Edited July 30, 2023 by RobH Quote Link to post Share on other sites
Drewmotty Posted July 30, 2023 Report Share Posted July 30, 2023 The common denominator is the earth connection so I’d look there. Maybe just hold a temporary earth to the housing to see if it heals up and test the theory. Quote Link to post Share on other sites
Lebro Posted July 30, 2023 Report Share Posted July 30, 2023 (edited) My 1st thought was bad earth, but Rogers test of a direct +ve wire from battery to sidelights defeats that possibility. I presume the sidelight, & indicator are separate (single "filament") bulbs ? Bob Edited July 30, 2023 by Lebro Quote Link to post Share on other sites
stuart Posted July 30, 2023 Report Share Posted July 30, 2023 We used to call that effect "Cross talk" but that was with high power electrics running next to microphone cables. I would say earth problem with the actual body of the lamp unit, or damp getting in. Stuart. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 30, 2023 Report Share Posted July 30, 2023 (edited) What voltage are you getting at the side lamp wire with an incandescent bulb? Not an high resistive contact in the light sw? Edited July 30, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
Andy Moltu Posted July 30, 2023 Report Share Posted July 30, 2023 Sounds like an earth problem. Is it both sides? The low current drawn by an indicator bulb shouldn't be enough to induce enough to light the side lights. Quote Link to post Share on other sites
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