Lotus Elan

probable earth problem

PostPost by: Watcombe » Wed Jun 04, 2014 7:11 pm

Electrics completely dead on Elan S4. Battery full charge, good live wire to solenoid (12.7v), new terminals. Nothing works except bit of a flicker in interior light when door opened, goes out if ignition switched on. I've checked all the earth connections I know about: under spare wheel, chassis to engine mount, behind cigar lighter - all ok. Any suggestions? Repeating myself here - first post didn't seem to go through.
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PostPost by: ricarbo » Wed Jun 04, 2014 8:25 pm

Assuming it's negative earth, put the positive lead of your multimeter (set to read dc voltage) to the earth side of whatever doesn't work. Connect the negative lead to a wire run from the battery negative terminal. When the item is turned on, there should only be a voltage reading of about 1 volt, hopefully less. If there is a bad earth route, you will get a higher voltage. With the item still turned on, try the positive probe of the multimeter at other points along the line to the battery negative terminal, until you find the two points where there is a big difference in voltage. That is where the bad connection is.
Use the same technique,measuring between the battery positive terminal and the non earth side of units to find a poor supply. Ideally all the battery voltage is seen across the positive and negative terminals of the unit when it is running. In practice, you won't achieve that.
As you work along the lines, cleaning the connections, reassemble them with something like Vaseline, to keep them cleaner and exclude air and moisture.
regards
Richard
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PostPost by: PeterK » Wed Jun 04, 2014 8:58 pm

And check the battery connections (remove, clean and refit)
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PostPost by: Watcombe » Fri Jun 06, 2014 7:28 am

Thanks so much for the helpful responses! Turns out a number of live connections in the wiring above the passenger foot-well, by the fan motor, had corroded and cooked themselves rather alarmingly at some point. So no power to ignition or anything else. Took a very lithe RAC guy to limbo-dance under there and reconnect them, and all's well. No way I could have done that!! And thank goodness it conked out rather than caught fire!
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