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alternator not charging battery

C

cerberusaardvark

Well-Known Member
Joined
September 7, 2009
Messages
331
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2
City, State
San Diego
Year, Model & Trim Level
1994 Explorer xlt
scratching my head here, my battery has died multiple times and my alternator doesnt charge it while the engine is running. i got a new stock alernator(95 amps) and i slow charged my battery overnight but in the morning i still had a low battery gauge while the engine was running. now i charge the battery every night but the the needle on the battery gauge never gets above the "n" in normal. i took out the battery and cleaned the terminals with sandpaper. when i drive longish distances i can actually watch the battery needle go down, especially at night.

the first time i was driving at night and my lights got dim, i lost power to my interior electronics and tachometer, and my engine sound like it was about to blow up and or meltdown. that spoke to me of alternator problems but the new one doesnt help at all.

I took it to ford but they tested the battery and said it didnt have a full charge and everything looked good.

why is my engine turning into an electricity zombie?
 



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Replace your cables. They tend to rot out. They may look ok, & not be.
 






I agree i had the same issue. I had to jump everytime i started the truck. Didn't matter how long i drove if i killed the engine, it would be dead. I pulled the old battery cables out and i had 4 separate breaks through the wire shielding from just rubbing on different parts.

After i replaced the wires i turned the key and it fired tight up. Its not that hard to do either.
 






You need to find out if the issue is not charging or if the issue is the battery is being drained overnight..

Charge the battery up and let it sit overnight.. if it dead in the morning (or much lower) then the battery is bad OR you have a drain when the vehicle is off.

If the above test pass then skip down to the Battery not charging section.. :)

Next, charge up the battery and disconnect the negative cable and check it in the morning.. If its low/dead its the battery.. If not, you know its a drain.

Next is to charge the battery and put a DC Amp meter between the battery and the negative cable. You want to see a very very very minute drain or no drain. If you see 1 Amp or more something is pulling power that shouldn't. Start pulling fuses to find it..

I'd start with Fuel pump Fuse, then any lighting fuses (including the one for the glove box light)..

Once you find the fuse that makes the drain go away you know "around" where the issue is..

Battery not charging section :)

If the battery isn't charging take your DVM (digital volt meter) and put it on DC volts (20v scale). Now measure from the negative battery post to the positive when the truck off and running. The voltage will probably be the same or lower when the truck is running which indicates a problem.

Now measure between the negative battery post and the big lug on the back of the alternator. If you see the voltage is higher then the alternator is trying to charge but the wire is broken between the alternator and the battery (possibly a blown fusable link).

If the alternator isn't "trying" to charge then look for the alternator fuse (I think its under the hood) AND make sure the bulb in the dash for the charge light is good. If either is bad the alternator won't get excited and won't charge..

Ok, enough rambling.. Good luck..

~Mark
 






updates...just got done with some cable replacement. i replaced the positive cable because i could see some sections where the sheathing had come loose and exposed the red insulation... but that didnt solve my problem. didnt think it would but you never know about the corrosion concealed beneath the rubber. tomorrow im going to pull the alternator cable, the one that runs from the starter to the plugs on the back and start looking for breaks.
 






HI BUCK HERE,, ONE THING ID ADD,, with a known fully charged abttery,, turn ign switch off,, remove either cable removed,, test for voltage between batt post and cable with that dvm, that is with every thing off, doors closed, any voltage shows voltage being drawn off,,no voltage=no drain, buck,,,,,,
Maniak said:
You need to find out if the issue is not charging or if the issue is the battery is being drained overnight..

Charge the battery up and let it sit overnight.. if it dead in the morning (or much lower) then the battery is bad OR you have a drain when the vehicle is off.

If the above test pass then skip down to the Battery not charging section.. :)

Next, charge up the battery and disconnect the negative cable and check it in the morning.. If its low/dead its the battery.. If not, you know its a drain.

Next is to charge the battery and put a DC Amp meter between the battery and the negative cable. You want to see a very very very minute drain or no drain. If you see 1 Amp or more something is pulling power that shouldn't. Start pulling fuses to find it..

I'd start with Fuel pump Fuse, then any lighting fuses (including the one for the glove box light)..

Once you find the fuse that makes the drain go away you know "around" where the issue is..

Battery not charging section :)

If the battery isn't charging take your DVM (digital volt meter) and put it on DC volts (20v scale). Now measure from the negative battery post to the positive when the truck off and running. The voltage will probably be the same or lower when the truck is running which indicates a problem.

Now measure between the negative battery post and the big lug on the back of the alternator. If you see the voltage is higher then the alternator is trying to charge but the wire is broken between the alternator and the battery (possibly a blown fusable link).

If the alternator isn't "trying" to charge then look for the alternator fuse (I think its under the hood) AND make sure the bulb in the dash for the charge light is good. If either is bad the alternator won't get excited and won't charge..

Ok, enough rambling.. Good luck..

~Mark
Click to expand...
 






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