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2004 Safari RWD, 2002 Astro AWD
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How long do you keep your van parked before driving it . 1 or 2 weeks regularly or more?
If you do that often enough then the battery will be run down and not hold the charge well, then the alternator is working hard to bring it up.
Before you start the van, measure the battery voltage.
A 80, 90 to 100% battery charged up should measure on hand held meter 12.42,12.5 to 12.7 vdc
 

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1998 LS AWD Forest Green metallic
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1,327 Posts
Hi

My voltage reading is under 14. Battery (2 years in good shape) and brand new alternator. No starting problems, no battery drainage.

Do you have any idéal?

Thanks a lot
I do not trust the factory voltmeter, and pay little attention to the actual number on the dial. It is for 'relative' readings.
You need to measure actual battery voltage with a decent meter. Do that with the key on, but the motor off. Compare the factory voltmeter, with the and held meter, for reference. Then do the same with the motor running.
Now you have a reference so you know what the factory meter is actually telling you, and you have a basis for discussion.
Rod J.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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5,998 Posts
You drew an incomplete picture:
  • Were readings hot or cold?
  • Were readings idling or cruising?
  • Were readings under heavy current load?
  • Are your readings suddenly different than normal?
  • What is the condition of your battery?
All these will affect the voltage reading at this gauge.

As stated, this gauge is not highly accurate, and should be considered for relative readings. If you have concerns and the readings seem suddenly lower than normal, you should take accurate readings with a voltmeter at the battery. Voltages at battery should be:
  • Engine OFF: 12.8v (typical)
  • Engine ON: 14v (typical) (13-14.5v depending on load, temperature, rpm)
1) Readings are typically higher cold when first started (14v), and tend to drop a little after warming up (13.5v).
2) Output of alternator is typically lower at idle, and will go up with more throttle when loaded.
3) Output and voltage reading will be affected by loads such as A/C (or dual A/C units) and electrical fans. Warmed up at idle, it is possible that the A/C system may pull move power than the alternator is producing. The output will go up when you increase rpms and start cruising.

As I've shown, there are many variables that can affect your readings.
4) But if the readings are suddenly different than normal, you may have an issue.
It is possible also, that the alternator may have become weak, charging adequately under light load and falling short under heavier loads.

5) Finally, be sure to check battery condition, which could affect your overall readings as well
 

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Discussion Starter · #7 ·
Wow great responses!!! I noticed that it is when i put the blower on max that it drops. Also, i upgraded my alternator for a 145amps instead of a 105 stock. Still difficult to keep a steady voltage. I Will check my readings with a voltmeter like you said. The big 3 will be necessary as i understand.
 

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1998 LS AWD Forest Green metallic
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Wow great responses!!! I noticed that it is when i put the blower on max that it drops. Also, i upgraded my alternator for a 145amps instead of a 105 stock. Still difficult to keep a steady voltage. I Will check my readings with a voltmeter like you said. The big 3 will be necessary as i understand.
MM is spot on, with his comments.
If the voltage drop condition is when the electrical system is under a good load, as you seemed to indicate, I would not be too concerned. But, having some known reference points to compare to a decent voltmeter, will give you some piece of mind.
 

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1998 LS AWD Forest Green metallic
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1,327 Posts
Am I missing a post or something? What is “big 3 upgrade"?
Search on 'Big 3 upgrade'.
It is referring to upgrading heavy current cables from alternator to battery, battery to engine, and battery to frame. It is a desirable upgrade if you are doing the big alternator ( AD244) install, or have a lot of power hungry add-ons.
Rod J
Issaquah, WA
 
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You drew an incomplete picture:
  • Were readings hot or cold?
  • Were readings idling or cruising?
  • Were readings under heavy current load?
  • Are your readings suddenly different than normal?
  • What is the condition of your battery?
All these will affect the voltage reading at this gauge.

As stated, this gauge is not highly accurate, and should be considered for relative readings. If you have concerns and the readings seem suddenly lower than normal, you should take accurate readings with a voltmeter at the battery. Voltages at battery should be:
  • Engine OFF: 12.8v (typical)
  • Engine ON: 14v (typical) (13-14.5v depending on load, temperature, rpm)
1) Readings are typically higher cold when first started (14v), and tend to drop a little after warming up (13.5v).
2) Output of alternator is typically lower at idle, and will go up with more throttle when loaded.
3) Output and voltage reading will be affected by loads such as A/C (or dual A/C units) and electrical fans. Warmed up at idle, it is possible that the A/C system may pull move power than the alternator is producing. The output will go up when you increase rpms and start cruising.

As I've shown, there are many variables that can affect your readings.
4) But if the readings are suddenly different than normal, you may have an issue.
It is possible also, that the alternator may have become weak, charging adequately under light load and falling short under heavier loads.

5) Finally, be sure to check battery condition, which could affect your overall readings as well

This! Mmusicman lays it down folks.
 

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Common Sense + Critical Thinking
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14,037 Posts
I wouldn't stress about it too much if it's not causing problems. Definitely put a meter on it and see exactly what your voltage readings are at the battery. "Big 3" probably isn't necessary but might think about at least the power lead from the alternator esp if you are charging a house battery/bank or have upgraded to electric fans/etc.
 
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