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#1 |
Registered User
Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Need Help! Alternator problem/charging issue
Ok so I have a 1970 c10 with a 350-hei internally regulated Alternator. I can jump it off and it runs until I shut it off. Thought tge battery was weak so I changed it. That did not work. I thought maybe I didn't have a good connection back to the battery-wired through the starter, so I added a wire directly to the battery, still having issues. I then thought maybe the alternator was wired wrong-the wire to the ignition, so I ran a new wire to the ignition. Still n o result. I then thought maybe the alternator was weak, so I changed it, still no difference. Any ideas?
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Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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#2 |
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Join Date: Oct 2013
Location: Schaghticoke NY
Posts: 77
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Re: Need Help! Alternator problem/charging issue
That is a very simple alt to wire. Large post goes directly to the battery. From the large post make up a jumper wire to go to one of the two prongs on the connector. The other prong gets switched power. you should be putting out about 14.5 volts.
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69 Chevy C10 Fleetside Long box |
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#3 |
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Location: Centrally located between Houston, Austin and Waco. BCS area.
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Re: Need Help! Alternator problem/charging issue
Need a little more info. You say it will start fine if you "jump it off" -I'm assuming jumper cables to battery posts -and you replaced the battery and alternator. If the battery has a full charge it should start the engine without jumpering.
If it's draining off while running, the alternator is either wired wrong or it's still bad. If that's the case, check the voltage from plus to negative battery posts with a voltmeter while it's running. It should be anywhere between 13.5 to 15 vdc. If it's not, check your wiring again and put a good charge on the battery to see if it will start the engine without jumpering (eliminates it being bad).
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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#4 |
Active Member
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Location: Centrally located between Houston, Austin and Waco. BCS area.
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Re: Need Help! Alternator problem/charging issue
Check with this wiring diagram.
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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#5 |
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Join Date: Jun 2010
Location: Upland Ca
Posts: 4,143
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Re: Need Help! Alternator problem/charging issue
Have you load tested the battery?
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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#6 | |
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Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Re: Need Help! Alternator problem/charging issue
Quote:
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Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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#7 |
Registered User
Join Date: Nov 2012
Location: Wasola, mo
Posts: 163
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Re: Need Help! Alternator problem/charging issue
So with jumpers it always starts right up?...If it was me i would go get a one wire alternator and try that. That would eliminate most wiring issues, but that's just me. Def sounds like a alternator issue.
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#8 |
Registered User
Join Date: Oct 2013
Location: Schaghticoke NY
Posts: 77
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Re: Need Help! Alternator problem/charging issue
When you jump it are you hooking the negative jumper on the dead truck to the battery or the engine as a ground? if your hooking it to the engine you may have a bad ground to the block.
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69 Chevy C10 Fleetside Long box |
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#9 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Need Help! Alternator problem/charging issue
I can't promise this won't hurt anything, but if you unplug the alternator while the truck is running, does the idle speed up, like a load has been taken off? And is the alternator hot?
Often, if a diode pack goes, it will be basically a short circuit inside the alternator. Your description though makes it sound like it will never restart unless you're boosting it, regardless of the state of the battery. If that's the case, if there were some safe way of boosting it with the cables hooked right to the battery, and if it then didn't crank, you'd know it was a connectivity issue with your battery cables. Since I'm going to guess you're hooking up the negative booster cable to the engine, I'm going to wager that you have a bad ground between the engine and the frame/battery. To test this theory, just use the black cord of the jumper cables to connect your (charged) battery's negative post to a good ground on the engine. If that fixes it, you've found your problem and need to fix the ground.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#10 | |
Active Member
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Location: Centrally located between Houston, Austin and Waco. BCS area.
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Re: Need Help! Alternator problem/charging issue
Quote:
Seems to me that if you have tried three fully charged batteries and it won't even crank except by jumpering there's something definitely not right. Don't know what, but it should at least turn the engine over. Remember, all you're doing by jumpering is bypassing a weak battery that's not fully charged. Got to be some really bad connection somewhere.
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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#11 | |
Registered User
Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Re: Need Help! Alternator problem/charging issue
Quote:
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Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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#12 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: Need Help! Alternator problem/charging issue
It sounds like your starter is drawing to much current.
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#13 |
Registered User
Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Re: Need Help! Alternator problem/charging issue
What would cause my starter to draw too much current and how do I correct it?
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Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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#14 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,151
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Re: Need Help! Alternator problem/charging issue
1-wire alternators are not the best for a street application. They are best suited for machinery and other low amperage applications. Because of the 1-wire configuration you lose the ability to sense load and they don't recover as fast as a 3 wire configuration.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#15 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: Need Help! Alternator problem/charging issue
A defective starter will draw to much current. They can weaken a battery. A shorted alternator can drain the battery and still charge.
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#16 |
Registered User
Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Re: Need Help! Alternator problem/charging issue
well it turns out the wire going to the starter had melted against the manifold. honestly i am lucky it didnt catch fire. disaster missed and charging correctly now. I drove it all week with no issues and it cranks right up
__________________
Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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