gordonmckerracher_2866 Posted June 22, 2015 Report Share Posted June 22, 2015 Can anyone advise on how to earth the number plate light on a MK 4 1972 Spitfire. This is the double light with Triumph logo. I have two live wires (one to each bulb). How is it earthed? Is it through the lamp body to the bumper? Link to comment Share on other sites More sharing options...
KevinR Posted June 22, 2015 Report Share Posted June 22, 2015 In the usual Triumph style, earths are via the metalwork - fingers crossed that there is no corrosion, and that a bolt somewhere is done up tight enough to cut through any paint. It is good practice to run a separate earth wire to a convenient bit of bare metal on the body tub. 1 Link to comment Share on other sites More sharing options...
gordonmckerracher_2866 Posted June 22, 2015 Author Report Share Posted June 22, 2015 Kevin.......Many thanks for your response. Where on the lamp holder would you attach the earth or is this just done via the bolt into the bumper? The base of the lamp holder where the bolts fix to the bumper seems to be "pot metal" and not sure if if would conduct very well. There is no wiring diagram that I have found that shows an earth for this. Plus would this not make the lamp holder and bumper "live"? As you can gather I'm not an electrician! Link to comment Share on other sites More sharing options...
KevinR Posted June 22, 2015 Report Share Posted June 22, 2015 The earth already goes through the base plate via the "pot metal", through the studs holding it to the bumper, hoping that the corrosion arround them doesnt cause a problem, then via the bumper into the bolts holding the bumper to the body, and into the body, again hoping that the paint has been scratched away enough when the nut was tightened against the lock washer for the bumber to make an electrical connection with the body. Attaching a wire anywhere on the base plate will do, and it will not make things "live" as its the earth. Link to comment Share on other sites More sharing options...
gordonmckerracher_2866 Posted June 22, 2015 Author Report Share Posted June 22, 2015 Kevin.......got it. Many thanks for your help......Regds Link to comment Share on other sites More sharing options...
dougbgt6 Posted June 22, 2015 Report Share Posted June 22, 2015 And another thing! Olden times bulb holders were single wire and the body of the holder was earth, reaching earth through the metal work of the container. Modern bulb holders are two wire, requiring both live and earth connections. If you ever have to replace an old one you'll have to run an additional wire to earth. Link to comment Share on other sites More sharing options...
gordonmckerracher_2866 Posted June 22, 2015 Author Report Share Posted June 22, 2015 Doug.......Yes I have an old double bulb holder......one live wire to each bulb.......I have cleaned it up as best I could but, If it grounds ok as is I'll be surprised. I'll probably need to solder an earth wire to each holder and run them to a solid earth connection.....Thanks Link to comment Share on other sites More sharing options...
KevinR Posted June 22, 2015 Report Share Posted June 22, 2015 I believe that the "modern" bulb holders for the Spitfire - http://www.rimmerbros.co.uk/Item--i-RS2018 - have an extra terminal fitted for the earth. The holders with the earth were introduced for the T2000, and the traders now generally only stock the ones with an earth - which means you need to add earth leads to the lights when fitting them, but it gives a much more reliable earth compared to the original spitfire bulb holders. Link to comment Share on other sites More sharing options...
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