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99 monte carlo 3.1 wont hold charge.


michael33n

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Purchased and it wouldn't run unless jumper cables were attached. Had it holding charge for two days now it will drain battery but if I give it gas it goes up a few specs then drains again. Guy put new alternator new battery new belt on and a few wires under the fuse block.  I plan on having the alternator tested today if I can make it there. I have a multimeter so any ideas would help and be appreciated 

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What is the battery open-circuit (no-load) voltage?  A fully-charged battery will show 12.6--12.7 volts.

What is the charging voltage when the engine runs?  Typically, a GM will show 14+ volts at the alternator output stud, with the ground for the meter touching the alternator housing.

 

Loose/corroded battery cables, and/or defective cables are a strong possibility.  Cables are known to corrode under the insulation leaving almost no copper "conductor" in place.  But it looks fine from the outside.  Voltage-drop testing can find those problems.

 

 

Starter Voltage Drop Testing.JPG

Alternator Voltage Drop Test.JPG

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