I have 2002 Subaru Impreza WRX. The alternator went, so I replaced it. The voltage gauge was jumping up and down when fans kicked on and when I turned on accessories. I figured the alternator was messed up. Sent it back and got another one. Installed it and it still did the same thing. I checked all the grounds and power cables, cleaned them all: still does it.

I have an aftermarket stereo in my car with old alternator before it went. Lights never dimmed or volts never jumped same with accessories. The volts always stayed around 14. Now my voltage gauge drops to 12 and at times jumps to 15+ volts. I thought maybe battery and put new battery in now. Lights don't dim as much but voltage gauge still jumps. I took to Autozone. Their tester said the volt regulator was bad. Took it to Advanced for a second look. They said everything was fine, but at the time it was staying at 14 on my voltage gauge. It wasn't jumping around. Finished the test and it started doing it again. dropped to 12v then jumped up to 14 again. Is there anything else that can cause this beside alt and battery in a car?

  • Welcome to Motor Vehicle Maintenance & Repair! Please be kind when you post and use some punctuation so your post is human readable. I've gone through and edited your post to hopefully accomplish that. Aug 15, 2018 at 0:29
  • Low idle speed? bad alternator case ground? Crappy AM parts? What testing have you done other than get conflicting (bench test?) results?
    – Ben
    Aug 15, 2018 at 0:32
  • regular idle nothing on it sits at around 14 fans kick on it drops with all accessories on at idle it drops to about 12.6 12.4 i ran a ground from alt case too thinking bad ground was the problem . when i check with multimeter i get .07 from bat and case when i look everything up says supposed to be .05. Aug 15, 2018 at 1:13
  • I realise you've already replaced the battery but it may be worth attaching it to a battery charger overnight to ensure that the battery is at optimum charge. Aug 15, 2018 at 10:36
  • yes the batt is good. Just bought it before writing post lol .So i went to a alternator shop close to me, he swore it was the alt .Returned that one and bought one from him.He swore it would fix the issue. Nope sure didn't . Same exact issue.I just don't get it.All my grounds are good.He tested everything said it wasn't my wiring or grounds Aug 16, 2018 at 2:39


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