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post #1 of 4 (permalink) Old 04-15-2017, 09:55 PM Thread Starter
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Trans Am low voltage

OK, so as the title states I am having low voltage issues. My alternator was reading 13.8 and my battery was reading 13.6 during idle. I would hop in my car and my radio would say 12 volts. If I had any accessories on then it would sometimes drop as low as 10 volts. I thought that the radio voltage reading wasn't correct. I popped it out and tested voltage and they did match. So, the reading is accurate. I then had my alternator tested while I was at Oreilly one day and they said I had a bad regulator. I replaced it and now reads 14.2 alternator and battery, but still very bad voltage at the radio. I had an aftermarket system, but ripped it out when I noticed the bad voltage so everything is back to stock. I have 4 gauge ground, and 4 gauge from alternator to battery. I resanded grounds. Any idea what would cause such a huge voltage drop? Is there a common problem? Any help would be appreciated
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post #2 of 4 (permalink) Old 04-16-2017, 07:13 AM
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Put red lead of your multimeter set to dc volts on large power wire of alt and other lead on a good ground. Run engine, read volts at idle. Have assistant start turning on power accessories until they all are on. Has the voltage at alt dropped way down, or is it still between 13.5 & 14.5 volts?

If voltage at alt is good and voltage in interior is low, you have resistance in wiring causing voltage drop or the readings there are wrong.

If voltage drops at alt, they could have given you a bad alt. But you could also have a parasitic power draw somewhere in system or a shorted wire or component.
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post #3 of 4 (permalink) Old 04-16-2017, 07:43 AM Thread Starter
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Already did the first part. I will try the second part with accessories. Is there any trouble areas to look for first? I have no idea where to start chasing grounds and wires
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post #4 of 4 (permalink) Old 04-18-2017, 02:27 PM Thread Starter
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Appears the alternator is outputting a little less with accessories but minor. Iso there any typical culprits when it comes to shorts etc? I double checked my radio and the main power is showing 11.7 while the accessory is showing 14v. It keeps dropping the louder I play the music and bottoms out around 10v.
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