Help! charging sytem acting weird! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C203/4 · 06-25-2008, 04:51 PM

i have an 84 chevy pu i replaced alternator, battery, negative cable, and continuity of all wiring for the alternator the system has only 12.5 volts when it is checked with a voltmeter, you disconnect the positive cable and the cable read 14 volts hook it back up to the battery and it goes back to 12.5 and the system only runs off the battery. have replaced the batery twice, not it, replaced the alternator with three of them all test good. with the key off and the positive cable off a test light going to the cable and the positive side of the battery doesnt light up so no drain on the battery any ideas?

OJOE · 06-25-2008, 06:44 PM

i guess i missed the problem your having. is your battery going dead?

**old Rusty C10** · 06-25-2008, 06:48 PM

the grounds are good? the connections at the starter ( cleaned well and no rust on the solenoid)? and the voltage regulator in the alternator is good?

C203/4 · 06-26-2008, 11:15 AM

Yes the problem i am having is the battery is not charging and slowly goes dead only 12.5 volts with sytem hooked up, take positive cable off battery 14.5 volts at the cable.

Grounds have been ground down to bare metal replaced negative battery cable, three grounds from battery, body, frame, motor, connections are good at starter too. brand new alternator, third alternator, it is a good one.

James McClure · 06-27-2008, 05:54 AM

C20. Eng off battery voltage 12.5 to 13 volts is normal. Eng running 14.5 to 15 is normal. Eng off, doors closed, key out of the ignition, parasitic load of 50 to 75 MA, normal. ( will not light a test light in series with a disconnected battery cable) Does vehicle meet these specs? Disconnect the alternator, both red wires should be hot with key on or off. Brown wire will only be hot with key on. OK? If either red wire is cold, check ALL the fuse links. 2 or 3 at the starter "B" term and 1 up on the firewall a few inches to the passengers side of the brake booster on a terminal block. Turn the key on and check the brown wire at the alternator, it should get hot. If not, check guage fuse, and while your there, check them all. My thoughts are you'll find a fuse link burned out. To check a fuse link get ahold of the large black plastic piece on the wires at the starter or terminal block and give them a pretty solid tug, if they are bad they will break. To replace them, cut behind the black lug on the wire and using heat shrink crip connector, replace with fuse link wire, crip in and heat with a ciggaret lighter. Wal-Mart has the connectors. Use 10 guage wire and the yellow connectors. Same goes for the "eyelet" end of the wire, yellow with a hole in the eylet big enough for a 3\8" bolt. If you find a burned out link, find the cause before you replace it, obvious right? LOL. Keep us informed. If you need more info drop me a line at "jmcclur2@nycap.rr.com". I'll send you my number by return mail and you can call me. Good luck, jim

06-25-2008, 04:51 PM	#1
C203/4 Registered User Join Date: Oct 2006 Location: Austin Texas Posts: 60	Help! charging sytem acting weird! i have an 84 chevy pu i replaced alternator, battery, negative cable, and continuity of all wiring for the alternator the system has only 12.5 volts when it is checked with a voltmeter, you disconnect the positive cable and the cable read 14 volts hook it back up to the battery and it goes back to 12.5 and the system only runs off the battery. have replaced the batery twice, not it, replaced the alternator with three of them all test good. with the key off and the positive cable off a test light going to the cable and the positive side of the battery doesnt light up so no drain on the battery any ideas?

06-25-2008, 06:44 PM	#2
OJOE Crew Cut Join Date: Dec 2005 Location: MONTGOMERY,AL Posts: 757	Re: Help! charging sytem acting weird! i guess i missed the problem your having. is your battery going dead? __________________ 85 SWB 1/2 TON CREWCAB/5.3 03 CHEV 3500 DURAMAX CREW CAB 85 CHEV SWB/TPI 06 CHEV TAHOE (WIFES) 30 MODEL A HOT ROD 07 HARLEY DAVIDSON BAGGER 09 STREET GLIDE AN D A LOT MORE JUNK

06-25-2008, 06:48 PM	#3
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: Help! charging sytem acting weird! the grounds are good? the connections at the starter ( cleaned well and no rust on the solenoid)? and the voltage regulator in the alternator is good? __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

06-26-2008, 11:15 AM	#4
C203/4 Registered User Join Date: Oct 2006 Location: Austin Texas Posts: 60	Re: Help! charging sytem acting weird! Yes the problem i am having is the battery is not charging and slowly goes dead only 12.5 volts with sytem hooked up, take positive cable off battery 14.5 volts at the cable. Grounds have been ground down to bare metal replaced negative battery cable, three grounds from battery, body, frame, motor, connections are good at starter too. brand new alternator, third alternator, it is a good one.

06-27-2008, 05:54 AM	#5
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Help! charging sytem acting weird! C20. Eng off battery voltage 12.5 to 13 volts is normal. Eng running 14.5 to 15 is normal. Eng off, doors closed, key out of the ignition, parasitic load of 50 to 75 MA, normal. ( will not light a test light in series with a disconnected battery cable) Does vehicle meet these specs? Disconnect the alternator, both red wires should be hot with key on or off. Brown wire will only be hot with key on. OK? If either red wire is cold, check ALL the fuse links. 2 or 3 at the starter "B" term and 1 up on the firewall a few inches to the passengers side of the brake booster on a terminal block. Turn the key on and check the brown wire at the alternator, it should get hot. If not, check guage fuse, and while your there, check them all. My thoughts are you'll find a fuse link burned out. To check a fuse link get ahold of the large black plastic piece on the wires at the starter or terminal block and give them a pretty solid tug, if they are bad they will break. To replace them, cut behind the black lug on the wire and using heat shrink crip connector, replace with fuse link wire, crip in and heat with a ciggaret lighter. Wal-Mart has the connectors. Use 10 guage wire and the yellow connectors. Same goes for the "eyelet" end of the wire, yellow with a hole in the eylet big enough for a 3\8" bolt. If you find a burned out link, find the cause before you replace it, obvious right? LOL. Keep us informed. If you need more info drop me a line at "jmcclur2@nycap.rr.com". I'll send you my number by return mail and you can call me. Good luck, jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.



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