Grahamgl Posted January 14, 2016 Report Share Posted January 14, 2016 Gentlemen, A question for the electrical experts on the Forum. I recently upgraded from a dynamo to a 45 amp alternator. As part of the upgrade I decided to fit a 50 amp ammeter. I had run the car prior to this using the 30 amp ammeter for a few weeks without a problem I removed the dashboard and, all of the instruments were removed. The battery’s negative lead was of course detached. I refitted the instruments and wiring. Before I re-fitted the dash I thought I would check that the instrument lights were working. I reconnected the battery, then turned on the lights. I must have touched a live terminal from on of the instruments to the metal dashboard as Lucas smoke appeared and the covering on the daisy chain earth started to burn. Turned of the lights and removed the battery lead, and a quick blast with a fire extinguisher, a matter of seconds from start to finish. The effect of the fire was that the daisy chain earth had lost its sheathing and the wires to the fuel gauge and temperature gauge and gauge lights had been scorched. This morning I made a new earth daisy chain and replaced the scorched lengths of the Green/Black, Green/Blue and Red/White wires. Before I carried on and replaced the dashboard I thought I would check the wiring I had replaced by doing a continuity check with my multimeter. With the red multimeter lead to the two Green/Blacks and then the Green/Blue wires with the black multimeter lead to one of the car’s earth wires there was no continuity. However, using the Red/White wire to an earth connection I found that there was continuity. I examined the part of the loom that contains the earth wires and the Red/White wires, I unwrapped about 6 inches of the loom, the leg off the main loom to the instruments, to look for damage there as well, non apparent. My question is, is the continuity I found on the Red/White wire normal or, have I got a short somewhere further up the loom caused by the Lucas smoke? Thanks for the advice. Graham Quote Link to post Share on other sites
RogerH Posted January 14, 2016 Report Share Posted January 14, 2016 Hi Graham, depending on what is connect the red/white wire will short to earth via the instrument bulbs. The bulbs are low ohms and quite a few in parallel make it lower. Roger Quote Link to post Share on other sites
Grahamgl Posted January 14, 2016 Author Report Share Posted January 14, 2016 Roger, The bulbs and holders have not been inserted into the insruments, just hanging loose. One probe of the multimeter was attached to one of the bulb holders, the other probe to an earth tag in the loom. This showed continuity. Graham Quote Link to post Share on other sites
RobH Posted January 14, 2016 Report Share Posted January 14, 2016 (edited) By measuring back through the rheostat you are probably seeing continuity throught the front and rear side-lights http://www.advanceautowire.com/tr24a.pdf edited because of cross-posting Edited January 14, 2016 by RobH Quote Link to post Share on other sites
RogerH Posted January 14, 2016 Report Share Posted January 14, 2016 Hi Graham, as Rob has hinted, the red white wire also goes the other way - through the Rheostat to the fuse holder and then down to the outside side lights etc Roger Quote Link to post Share on other sites
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