that__seth__guy Posted March 3, 2014 Report Share Posted March 3, 2014 Hey guys (and any gals), I have a 1971 Ford 302 in my 1968 Mustang (for background information), I have replaced ALL ignition components with MSD products. I have also put in a nice Retro-Sound stereo and LED tail lights along with upgraded headlights... my question IS: At idle, my battery voltage is 12.6v and with all lights on its 12.3v... is that too low? When I rev the engine above say 1,700RPM it comes up to 13v but at idle and in gear, its the 12.3v. I've had the battery tested, it holds charge. Should I replace the alternator with a higher output to compensate my MSD setup??? New Voltage regulator? Both? ANY input is requested and GREATLY appreciated!!!! -Thanks! Link to comment Share on other sites More sharing options...
08GT5004ME Posted March 13, 2014 Report Share Posted March 13, 2014 My son's 71 had a simular problem and after checking everything out we found a corroded ground between engine block and body, corroded wiring harness coming from the alternator. We had already had the alternator tested and found out it had a bad diode so it and the voltage regulator were replaced which helped but output was below normal until the ground and harness connections were cleaned. After that we had 12.9 at idle and up to 13.9 above idle. The repairs also eliminated most of the flickering of the lights even with the mechanical regulator. Link to comment Share on other sites More sharing options...
Don Johnston Posted March 13, 2014 Report Share Posted March 13, 2014 Same issue with late model classics here. Check all grounds for dirt, oil, corrosion and wire brush them clean. Also, the MSD unit doesn't like hot engine compartments and is more stable if relocated under the dash. If you upgraded your stereo, starter, fuel pump or any other electrical demands, you will need a stronger alternator. Going up a few amps always helps as the factory unit is pretty low on output. Also, what is your idle setting? You could go up 50 to 100 RPM if needed, especially if you upgraded the carb and intake. Link to comment Share on other sites More sharing options...
that__seth__guy Posted March 24, 2014 Author Report Share Posted March 24, 2014 Thanks for the quick replies! I checked all grounds and decided to clean everything and check for wire breaks first. After that didn't solve my problem, I took out the alternator and took the back off. One of my brass connections was off and actually being ground down... Went and picked up a new alternator for like $40 and that fixed the problem! Im happily idling at 13.4V! Even with every light on (including both turn signals) and the radio blaring, it idled at 12.8-12.9V!!! Problem solved! Link to comment Share on other sites More sharing options...
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