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Tiny
ZACHARY72$!
  • MEMBER
  • 2003 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 271,179 MILES
My dad has been a mechanic for over thirty years my question is that he could not even answer, is that when I have my truck running it reads 14.03 okay when I have the terminal off and read it, it is reading 12.54 which mean there is a ground somewhere. So I took every fuse out one by one every ten minutes and still nothing. I just do not know what it could be.
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Sunday, September 23rd, 2018 AT 3:33 PM

22 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening.

12 volts when? Did you remove the battery cable with the engine running?

Any other information is helpful for me to understand what you are doing.

Roy
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Sunday, September 23rd, 2018 AT 5:23 PM
Tiny
ZACHARY72$!
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Okay, since I saw that alternator was recharging properly I went ahead and took off the terminal of the negative side then I hook the positive amp unit tester on to it then I took the negative unit tester to the positive on the battery and it was drawing 12.54 amps. If the battery is not hooked up it shouldn’t be drawing anything but like 0.01 or 0.02?
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Sunday, September 23rd, 2018 AT 5:32 PM
Tiny
ASEMASTER6371
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Okay, much better.

It sounds like you have your volt meter in volts, DC.

Check your setting to DC amps. There should be 50-75 milli amps max.
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Sunday, September 23rd, 2018 AT 5:40 PM
Tiny
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Alright, so I went back to the shop and put it on DC it is readying 10. So I went ahead a removed every fuse one by one in the truck and inside the engine bay and nothing happened stayed the same. So I checked the alternator to see if there was a ground there and it was not that I have a ground I just do not know what it could be. I would really like to find it I have a GMC Sierra 1500 2003 with 271,174.
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Monday, September 24th, 2018 AT 2:41 PM
Tiny
ASEMASTER6371
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Okay,

10 what? Did you disconnect the big wire at the back of the alternator?

Roy
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Monday, September 24th, 2018 AT 2:46 PM
Tiny
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0.010 amps. I am guessing. Yes I did that yeah.
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Monday, September 24th, 2018 AT 2:47 PM
Tiny
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When is on dc it is reading 0010.
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Monday, September 24th, 2018 AT 2:48 PM
Tiny
ASEMASTER6371
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Okay, then that reading is good..010 is below the spec. That is a good reading.

You still have a charging system issue with high voltage. You need to replace the alternator.

Roy
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Monday, September 24th, 2018 AT 2:54 PM
Tiny
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Yeah, but if my alternator is recharging properly how would that be the problem?
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Monday, September 24th, 2018 AT 2:55 PM
Tiny
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It could be a ground wire somewhere or the stater or something else.
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Monday, September 24th, 2018 AT 2:56 PM
Tiny
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Sorry, I thought it read 16.5 volts.

Senior moment.

The alternator is good.

What concern do you have about the system?

Roy
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Monday, September 24th, 2018 AT 2:59 PM
Tiny
ZACHARY72$!
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Okay, if the the alternator is charging properly and the fuses are good from inside the engine bay and inside the cab and the battery is brand new just got yesterday. That means there is a ground wire somewhere in the electrical in the engine bay somewhere I just do not know what to look at first.
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Monday, September 24th, 2018 AT 3:02 PM
Tiny
ZACHARY72$!
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Because a ground wire could be anywhere.
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Monday, September 24th, 2018 AT 3:03 PM
Tiny
ASEMASTER6371
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Okay, you are not understanding the system. Just because you have 12.4 volts on the negative cable does not mean there is a draw. Voltage is pressure. It needs to go to all the components. Voltage does not cause a battery drain. Current draw is what drains the battery. You have little or no current flow so the system is good.

You can have voltage with no current draw which is what you have right now.

The reading you get is normal and is not an indication of a ground, just pressure to components.

Roy
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Monday, September 24th, 2018 AT 3:07 PM
Tiny
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What should I do then? And the 12.4 volt was my battery for AC.
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Monday, September 24th, 2018 AT 3:10 PM
Tiny
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How do I relieve some of that pressure to the components?
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Monday, September 24th, 2018 AT 3:11 PM
Tiny
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What should you do about what? What is your concern? What am I missing?

Roy
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Monday, September 24th, 2018 AT 3:12 PM
Tiny
ASEMASTER6371
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You cannot. That is how the system was designed and how it operates. There is nothing you can do to change that.

Roy
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Monday, September 24th, 2018 AT 3:13 PM
Tiny
ZACHARY72$!
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Alright, let’s take a few steps back. Okay, I checked my charge for my alternator with AC I had right at 14.00 volts. Okay, then I took the negative side off then checked the battery for AC, I was getting 12.54. Okay, then I switched it to DC and it was drawing 0.010 volts which is not good because it should only being drawing about 0.01 or 0.02.
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Monday, September 24th, 2018 AT 3:15 PM
Tiny
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Battery for AC? Please explain.

The draw is fine.

.01 is the same as.010. That is not a problem.

Roy
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Monday, September 24th, 2018 AT 3:20 PM

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