Alternator question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SWINGSAX68 · 06-27-2002, 10:44 AM

the guy that is doing the engine work on my truck told my dad that one of the wires that carries the charge to recharge the battery doesn't have current, and the battery isn't getting charged. which wire does this? there is a BLUE, WHITE, RED, and BLACK, I think the Black wire is the ground so I grounded that one, but tell me what those wire do guys!!!!!

my new 72 · 06-27-2002, 10:50 AM

It should be the red one. Atleast it is on my truck. It should be connected to the positive battery cable. I'm not sure why it woldn't be getting juice though. Check all the connections at the alternator. If everything is plugged in then maybe the output from the alternator is bad, try a new one. If it doesn't fix the problem you can always take it back.

Blue68 · 06-27-2002, 11:11 AM

You should pretty much ALWAYS have a charge on the red wire on the back of the alternator. Its bigger one with it's own post. I say almost always because unless you take out the battery or disconnect it from the circuit there should be a charge. If your alternator is charging, you will get around 13.5 volts versus the nominal 12 from your battery. If you have melted a fusible link you won't see anything or your regulator is dead you won't either.

Now might be the time to go a one wire setup.

SWINGSAX68 · 06-27-2002, 12:26 PM

Get a new one???? Like a new Alternator????......Let me cal lmy dad up and see if the problem is fixed already, and I'll get back to you all....I'll fix er yet!!!!!!!! Does it matter where the black wire goes, I know on my girlfreinds truck, it isn't even placed any where just hanging loose.....

busterwivell · 06-27-2002, 03:38 PM

An easy way to test an alternator is (with engine running) put the tip of a screwdriver at the bearing at the center of the back of the alternator. If you feel a little magnetic pull, it's charging. No pull, no charge.

my new 72 · 06-27-2002, 03:41 PM

Yes a new alternator.

CE20934 · 06-28-2002, 02:56 AM

It matters where that black wire goes. In theory, the negative diodes will ground through the alternator case back to the battery through a few other parts. In the real world, they do no such thing, especially when there's much rust on each and every attaching point. Damn near got electrocuted by the alternator in my buddy's Caprice because there was no ground wire.

A properly attached ground wire makes the alternator run a bit cooler and more efficiently as well.

06-27-2002, 10:44 AM	#1
SWINGSAX68 Now the others dig........ Join Date: May 2002 Location: San Antonio, TX Posts: 1,520	Alternator question the guy that is doing the engine work on my truck told my dad that one of the wires that carries the charge to recharge the battery doesn't have current, and the battery isn't getting charged. which wire does this? there is a BLUE, WHITE, RED, and BLACK, I think the Black wire is the ground so I grounded that one, but tell me what those wire do guys!!!!! __________________ 68 Chevy C10 Stepside Black Primer 78 GMC Longbed White 09 Chevy Silverado Shortbed Granite Blue *LOOKING FOR A 67 4 DOOR IMPALA!!!Just like Sam and Dean Winchester!! 'Cause Mustangs are for p^#$ and you can fit a body in the trunk of a 67 Impala* MEMBER OF THE DRUM BRAKE CLUB Bachelor of Music in Jazz Studies Texas State University-San Marcos, TX Certified Music Educator I hope Mom is up there watching and being my Guardian Angel "I've got a fever.....and the only prescription.....IS MORE COW BELL" -The Legendary: Bruce Dickenson "F#$@ 'em up!!!!!!" -The Legendary: Rogelio Escobar TRUCKY LINKS** http://67-72chevytrucks.com/vboard/s...d.php?t=457750 http://67-72chevytrucks.com/vboard/s...d.php?t=461184 http://67-72chevytrucks.com/vboard/s...d.php?t=472848 http://67-72chevytrucks.com/vboard/s...d.php?t=417541 http://67-72chevytrucks.com/vboard/s...d.php?t=477788

06-27-2002, 10:50 AM	#2
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	It should be the red one. Atleast it is on my truck. It should be connected to the positive battery cable. I'm not sure why it woldn't be getting juice though. Check all the connections at the alternator. If everything is plugged in then maybe the output from the alternator is bad, try a new one. If it doesn't fix the problem you can always take it back. __________________ I'm going to Law School, wanna debate? It's good practice.

06-27-2002, 11:11 AM	#3
Blue68 Registered User Join Date: Apr 2000 Location: Frisco, Tx, USA Posts: 606	You should pretty much ALWAYS have a charge on the red wire on the back of the alternator. Its bigger one with it's own post. I say almost always because unless you take out the battery or disconnect it from the circuit there should be a charge. If your alternator is charging, you will get around 13.5 volts versus the nominal 12 from your battery. If you have melted a fusible link you won't see anything or your regulator is dead you won't either. Now might be the time to go a one wire setup. __________________ http://home.comcast.net/~r.landrum/w...tos.html-.html '68 C-10 LWB, '98 Z-71 350 w/accessories (Serpentine), Edelbrock Performer, Edelbrock 1405 (600cfm) carb, GM HEI, CompCam Extreme 4x4 roller cam, Thorley Headers, Carter Electric Fuel Pump, Vintage Air, 700r4, 3.73, disc brakes and power steering upgrades.

06-27-2002, 12:26 PM	#4
SWINGSAX68 Now the others dig........ Join Date: May 2002 Location: San Antonio, TX Posts: 1,520	Thanks! Get a new one???? Like a new Alternator????......Let me cal lmy dad up and see if the problem is fixed already, and I'll get back to you all....I'll fix er yet!!!!!!!! Does it matter where the black wire goes, I know on my girlfreinds truck, it isn't even placed any where just hanging loose..... __________________ 68 Chevy C10 Stepside Black Primer 78 GMC Longbed White 09 Chevy Silverado Shortbed Granite Blue *LOOKING FOR A 67 4 DOOR IMPALA!!!Just like Sam and Dean Winchester!! 'Cause Mustangs are for p^#$ and you can fit a body in the trunk of a 67 Impala* MEMBER OF THE DRUM BRAKE CLUB Bachelor of Music in Jazz Studies Texas State University-San Marcos, TX Certified Music Educator I hope Mom is up there watching and being my Guardian Angel "I've got a fever.....and the only prescription.....IS MORE COW BELL" -The Legendary: Bruce Dickenson "F#$@ 'em up!!!!!!" -The Legendary: Rogelio Escobar TRUCKY LINKS** http://67-72chevytrucks.com/vboard/s...d.php?t=457750 http://67-72chevytrucks.com/vboard/s...d.php?t=461184 http://67-72chevytrucks.com/vboard/s...d.php?t=472848 http://67-72chevytrucks.com/vboard/s...d.php?t=417541 http://67-72chevytrucks.com/vboard/s...d.php?t=477788

06-27-2002, 03:38 PM	#5
busterwivell Registered User Join Date: Jan 2002 Location: Sahuarita, AZ USA Posts: 2,033	An easy way to test an alternator is (with engine running) put the tip of a screwdriver at the bearing at the center of the back of the alternator. If you feel a little magnetic pull, it's charging. No pull, no charge. __________________ Bill - Tucson, AZ 47 Chevrolet 2 dr sedan 56 Chevrolet 210 2 dr sedan 66 Chevrolet Malibu 2 dr 4 speed 71 Chevrolet C30 Longhorn 86 Chevrolet Monte Carlo SS (Sold) 01 Chevrolet Tahoe IM - BUSTERWIVE@aol.com

06-27-2002, 03:41 PM	#6
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	Yes a new alternator. __________________ I'm going to Law School, wanna debate? It's good practice.

06-28-2002, 02:56 AM	#7
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	It matters where that black wire goes. In theory, the negative diodes will ground through the alternator case back to the battery through a few other parts. In the real world, they do no such thing, especially when there's much rust on each and every attaching point. Damn near got electrocuted by the alternator in my buddy's Caprice because there was no ground wire. A properly attached ground wire makes the alternator run a bit cooler and more efficiently as well. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed



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