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Charging system not working

Tiny
WAKA WAKA
  • MEMBER
  • 1996 CHEVROLET TRUCK
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 175,000 MILES
My truck is the 2500. Alternator not charging. I just got this truck and it has issues. Since battery warning light is not working will that keep alternator from charging. And another thing. Someone ran a jumper wire from ECM fuse (top side) to brown wire on alternator then to battery to make run. When hooked up the headlights stay on with switch in off position. Also, when I turn key off engine stays running. I could use charge system diagram and any help would be appreciated. Thanks
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Monday, June 12th, 2017 AT 11:24 PM

10 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Sounds like it may be a security issue and someone jumped the system to make it run. So try another key and then have it scanned for codes to see if it is a security issue. Finally check fusible links that go to alternator or maybe missing see diagram, also with this mileage replace belt and tension-er as recommended at 60,000 miles. The tension-er's lose tension and belt wears which you need a special tool to measure if worn not cracks in belt. Link runs off of battery not enough room to put on picture. There is also a gauge fuse in inside fuse box.
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Tuesday, June 13th, 2017 AT 6:12 AM
Tiny
WAKA WAKA
  • MEMBER
  • 5 POSTS
OK will do that. Also I took alternator in had it tested. OK. Got a new battery hooked them up and alternator charged 13.7 v. I believe I had it wired wrong though. White wire to gage and brown to battery. It charged for about a day and quit. Back to square one. Please let me know if I wired it wrong. Also truck won't start unless I run a jumper wire to under hood fuse block to cab fuse panel. I'm finding out that it doesn't really matter which one I hook jumper to it lights up instrument panel gauge's and it will start. Also when I do daytime running lights come on. How many volts does it take for alternator Excitor wire the tell alternator to charge. And if I have to can I run it from alternator straight to gauges fuse. Please let me know something and thanks so much.
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Sunday, June 18th, 2017 AT 2:17 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Actually if you look at the drawing I sent itshows how to wire as the connector will be marked as well.
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Sunday, June 18th, 2017 AT 7:17 AM
Tiny
WAKA WAKA
  • MEMBER
  • 5 POSTS
OK I had allternator tested again. This time bad. Bought a new one. Still noo voltage from lamp wire. I jumped exciter to battery for a sec and revved engine and alternator started charging for a few minutes and quit. I checked everything on instrument panel battery indicator fuse good bulb good but not lighting up. How can I wire this thing up to work. Is there another way. And is it just the lamp wire. I dont need sensor wire hooked up? Thanks so much
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Sunday, June 18th, 2017 AT 4:21 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
All of the wires need to be hooked up have you checked the fusible link and fuse that I have sent in drawing if the alternator is hooked up correctly per the drawing then it should work unless the wire is shorting out someplace in harness. Are battery terminals clean as it needs a good battery in order for alternator to work. Also check the main wire maybe that has rubbed through someplace causing a fail.
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Sunday, June 18th, 2017 AT 4:38 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Make sure the belt and tensioner are in good shape you can't check modern belts because of cracks. Recommended replacement is 60000 mi for both tensioner and belt. If you are still having problems this should be professionally looked at as I can't see this nor physically check it.
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Sunday, June 18th, 2017 AT 4:39 PM
Tiny
WAKA WAKA
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  • 5 POSTS
Belt is good just replaced. So you say all wires. I have batt hooked up brown wire to L white it says deisel only and other not used. Alt. Has SFLP so L is the only one on 4 prong plug hooked up Batt cables connections clean and good. Like I said no batt light in instrument panel still not charging. Any ideas
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Monday, June 19th, 2017 AT 12:13 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If the large wire is hooked up to the back for the armature and the brown wire to L then it is wired correctly check large wire to see if 12 volt with key on then check same at brown wire if it is then it may be the indicator if doesn't register not charging as gm indicators are notoriously bad. With engine at 1500 rpm check at battery if 13.7 volts that is ok. Also if you have the side terminals on battery remove bolt and check for heavy corrosion as they do that and don't charge well. Also if belt was replaced then tensioner should be also as they lose tension. Pink wire on drawing leads from ignition switch so that may not be getting power to indicator as well check at back of cluster where it plugs in.
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Monday, June 19th, 2017 AT 3:06 PM
Tiny
WAKA WAKA
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  • 5 POSTS
Can I wire up brown wire to something else and excite alternator. I think instrument cluster batt. Light wires in cluster it self is bad. Looks like there is a small tear in cluster plastic. And I do not have funds for new inst. Panel at present. Please let me know how I can wire up bi passing batt. Light
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Tuesday, June 20th, 2017 AT 8:19 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If you did this you would have to wire where it goes on and off with ignition. Check the pink wire for power going to cluster if no power then it may be a bad ignition switch
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Tuesday, June 20th, 2017 AT 8:21 AM

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