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2001 Chevey silverado not charging


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brokenchevy
Novice

Jul 19, 2018, 6:01 AM

Post #1 of 12 (422 views)
  post locked   2001 Chevey silverado not charging  

I have a 2001 Chevy Silverado with a 5.3. I replaced the alternator and now I am only getting 9 volts off the back of the alternator. I did bring it back and have it tested(it is good) and exchanged it. The fuse able link seems to be good and I'm getting 9 volts from the brown wire (voltage control PCM) I'm stumped what would be the next step


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 19, 2018, 10:34 AM

Post #2 of 12 (394 views)
  post locked   Re: 2001 Chevey silverado not charging  

9 volts is way too low. What is the voltage at the battery terminals. If it is 9 volts at the battery, have your battery checked and make sure it is fully charged. 9 volts at the battery is a fully discharged battery.

Once the battery is fully charged and checks good, recheck and let us know if we need to go further with diagnosing this.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jul 19, 2018, 10:43 AM)


brokenchevy
Novice

Jul 19, 2018, 10:56 AM

Post #3 of 12 (386 views)
  post locked   Re: 2001 Chevey silverado not charging  

The alternator and battery are new.
I recharged the battery and the voltage matches the battery on the alternator terminal


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 19, 2018, 11:03 AM

Post #4 of 12 (380 views)
  post locked   Re: 2001 Chevey silverado not charging  

If your only seeing 9 volts at the battery terminals, either your meter is incorrect or that battery is completely discharged. Does the engine crank over fine? It shouldn't even crank on 9 volts. Maybe check with another volt meter?





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brokenchevy
Novice

Jul 19, 2018, 11:11 AM

Post #5 of 12 (378 views)
  post locked   Re: 2001 Chevey silverado not charging  

No.. lol after charging the battery it tests at 12 volts. However the alternator still won’t charge and I’m running the car off the battery not the alternator. Thats how the new battery got to 9 volts.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 19, 2018, 1:17 PM

Post #6 of 12 (354 views)
  post locked   Re: 2001 Chevey silverado not charging  

Is the charging lamp warning indicator staying on in the DIC?

Are there any trouble codes stored in the PCM?

The grey wire at the alternator is the field circuit. The PCM controls the alternator's output by duty cycling the field control circuit. You might see that signal using your meter, but it will be an average voltage depending on how the PCM is commanding the field. Normally, if you lose the field signal, the regulator inside the alternator will default to a set voltage output. All checks should be make with the alternator connector plugged in and your meter negative probe on battery negative.

The brown wire is the lamp circuit. The regulator inside the alternator will ground that circuit if there is a charging system problem. The PCM sends battery voltage on the lamp circuit. If there is no voltage on the lamp circuit, the alternator won't charge. Be careful testing this because if the warning lamp is on, the regulator will be grounding the lamp circuit and you will see close to zero volts.

Take your meter and touch the alternator case and other probe to battery negative. You should see less than 0.5 volts. If you see battery voltage, you have a ground problem.

If all those things check out, you probably have a defective alternator.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


brokenchevy
Novice

Jul 19, 2018, 3:04 PM

Post #7 of 12 (349 views)
  post locked   Re: 2001 Chevey silverado not charging  

With the engine running and the negative lead of the voltmeter on the battery negative. I’m getting 0.8 volts to the brown wire and about 2 volts to the grey wire.
Does that mean PCM?


Discretesignals
Ultimate Carjunky / Moderator
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Jul 20, 2018, 7:23 AM

Post #8 of 12 (278 views)
  post locked   Re: 2001 Chevey silverado not charging  

The 2 volts on the grey wire is probably an average of the total voltage between 0 - 12 volts. The probably means the PCM is commanding the alternator. When you took the reading on the brown wire was the engine running or not. Is the charging light on when the engine is running?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


brokenchevy
Novice

Jul 20, 2018, 7:26 AM

Post #9 of 12 (276 views)
  post locked   Re: 2001 Chevey silverado not charging  

Yes the engine was running and the bolts light was flashing intermittently. There’s no codes in the OBD but I’m keeping in mind that the battery was removed


Discretesignals
Ultimate Carjunky / Moderator
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Jul 20, 2018, 12:56 PM

Post #10 of 12 (220 views)
  post locked   Re: 2001 Chevey silverado not charging  

Unplug the alternator connector and measure the voltage on the brown wire with the engine running.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


brokenchevy
Novice

Jul 20, 2018, 3:22 PM

Post #11 of 12 (208 views)
  post locked   Re: 2001 Chevey silverado not charging  

I think I got it fixed.
I went through the whole truck cleaned all the connectors including the PCM(they were corroded) tightened and tweezed a few things that bothered me along the way. Had the new alternator bench tested it was bed the second new one was bad out of the box so I went to another store (yeah I know I’m a slow learner) had that one bench tested before I left the store being paranoid and was wondering if my car was eating them. Installed the third alternator and bolts right around 14 maybe a little higher and no betttery light as of yet..
I just want to say thank you for all your time.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 20, 2018, 4:19 PM

Post #12 of 12 (195 views)
  post locked   Re: 2001 Chevey silverado not charging  

Glad to read that you got it fixed. 14 volts is normal for a charging system to be at. Sometimes the part stores house brand alternators have lots of defects. Usually we go with an AC Delco brand new unit on the Chevys at the shop I work at. I was figuring that if you had voltage sitting on the brown wire, the next course of action was to try different alternator. If you have any troubles let us know. Thank you for following up. I'm going to close this thread as solved. If you need it to be to reopened, just ask any moderator.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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