Charging

Tiny
TNARA
  • MEMBER
  • 1993 DODGE CARAVAN
  • 3.3L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 175,000 MILES
I replaced the alternator and charged the old battery start running the vehicle for a couple of days try to monitor the voltage it was over thirteen volts when not running and goes up to over fourteen when running it goes on like that for two days, but on the third day measure it up and the battery reading is only over five volts. Measure alternator the same reading. Call for service to replace the battery the guy check the reading it was over five volts, he check the alternator and it was okay. So we ran all the test and the system was okay, but as soon as he left it is back again to over five volts. What do you think seems to be the problem?
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Thursday, August 10th, 2017 AT 5:56 PM

4 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
Where is this five volts coming from? The engine cannot start or run with the battery voltage being that low. You cannot have thirteen volts on the battery either if the engine is not running. You might be measuring a "surface charge" if the battery was just being charged. Otherwise a fully-charged battery will read 12.6 volts.

What symptom are you trying to solve?
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Thursday, August 10th, 2017 AT 6:14 PM
Tiny
TNARA
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How will I know if my alternator is charging my battery when running?
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Thursday, August 10th, 2017 AT 8:44 PM
Tiny
TNARA
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I took the reading from the volt meter this morning like I said it was over 4 volts. My alternator is working and a new battery. Could it be my voltage regulator? Enclosed is an image of the voltmeter taking the reading while the van was not running. Also, I have no problem starting the engine.
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Saturday, August 12th, 2017 AT 1:22 AM
Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
I cannot quite see for sure, but it looks like the negative probe is on the battery's negative cable. If that is right, there is something wrong with your meter. I have about fifteen digital meters from my TV repair days, and one of them reads way wrong on all of the "DC Volts" scales. Find another battery to measure. If that one reads correctly, there is a film of black corrosion on one of the terminals in your photo that is interfering with the reading. It helps to poke really hard on the probes to get them to cut into good clean lead.

That battery should measure 12.6 volts if it's good and fully-charged. If it is good but discharged, it will read closer to 12.2 volts. If you find it at around 11 volts or less, it has a shorted cell and must be replaced.

To tell if the charging system is working, measure the battery voltage again with the engine running. It must be between 13.75 and 14.75 volts. I suspect that is what you have since you are not having a cranking problem.
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Saturday, August 12th, 2017 AT 8:09 PM

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