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

TheCougarine · 02-21-2016, 08:30 PM

Hey guys, so the alternator on my 71' is toast and I need to replace it but I really don't know very much about them so I'm kind of lost on what I need to buy. Could someone help me out and tell me what would be a simple bolt on replacement for the alternator on my truck? Thanks in advance.

57taskforce · 02-21-2016, 08:40 PM

I used a later model 64(?) amp Delco 10si internally regulated alternator. Is bolt on and with a few very simple wiring mods it by passes the external regulator system that the O.E. unit uses. They can be found on square body trucks amongst many other applications. They are readily available at the local parts stores.

davepl · 02-21-2016, 08:46 PM

I generally take an opportunity like this to convert to an internally regulated alternator, but if this one was meeting your needs before it failed, just get the direct replacement at your favorite parts store. Don't change anything.

If it -wasn't- putting out enough for your truck, read up on the conversions.

Stay away from the seduction of "one wire alternators". You lose a number of features, like the idiot light, field excitation, and so on. You have to (usually) rev them up to get them to start charging the first time too.

DTMsurf · 02-21-2016, 09:19 PM

I would just get the OE replacement from your nearest auto parts store. I'm running one and it is working just fine on my 72.

TheCougarine · 02-21-2016, 09:59 PM

One last thing, is it possible the voltage regulator is bad and causing the alternator to put out a low voltage? Is there a way to check that separately?

**71CHEVYSHORTBED402** · 02-21-2016, 10:28 PM

I'm replacing my perfectly good alternator for one internally regulated. Unfortunately I'm still using the one I have. Don't know about the wiring, but it doesn't matter anyway, because I'm replacing all that too.

davepl · 02-21-2016, 10:39 PM

Most auto parts stores can bench-test an alternator. If it's fine, then I'd suspect the regulator.

Growing up on the prairies where the next "big town" can be 6 hours away we used to carry spare belts, water pump, regulator, alternator, and fuel pump. Those are the "maintenance" items on a GM of that era.

02-21-2016, 08:30 PM	#1
TheCougarine Registered User Join Date: Sep 2014 Location: Johnson City TN Posts: 311	Alternator Replacement Question Hey guys, so the alternator on my 71' is toast and I need to replace it but I really don't know very much about them so I'm kind of lost on what I need to buy. Could someone help me out and tell me what would be a simple bolt on replacement for the alternator on my truck? Thanks in advance.

02-21-2016, 08:40 PM	#2
57taskforce All about them K’s Join Date: Jun 2014 Location: Land of Entrapment Posts: 6,487	Re: Alternator Replacement Question I used a later model 64(?) amp Delco 10si internally regulated alternator. Is bolt on and with a few very simple wiring mods it by passes the external regulator system that the O.E. unit uses. They can be found on square body trucks amongst many other applications. They are readily available at the local parts stores. __________________ Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne: 5” lift, 35’s, front dana 60 blah blah blah… http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB: 4” lift 33”s… in a million pieces http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 35x12.5x20’s Last edited by 57taskforce; 02-21-2016 at 09:01 PM.

02-21-2016, 08:46 PM	#3
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Alternator Replacement Question I generally take an opportunity like this to convert to an internally regulated alternator, but if this one was meeting your needs before it failed, just get the direct replacement at your favorite parts store. Don't change anything. If it -wasn't- putting out enough for your truck, read up on the conversions. Stay away from the seduction of "one wire alternators". You lose a number of features, like the idiot light, field excitation, and so on. You have to (usually) rev them up to get them to start charging the first time too. __________________ 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

02-21-2016, 09:19 PM	#4
DTMsurf Registered User Join Date: Feb 2016 Location: San Diego California Posts: 41	Re: Alternator Replacement Question I would just get the OE replacement from your nearest auto parts store. I'm running one and it is working just fine on my 72.

02-21-2016, 09:59 PM	#5
TheCougarine Registered User Join Date: Sep 2014 Location: Johnson City TN Posts: 311	Re: Alternator Replacement Question One last thing, is it possible the voltage regulator is bad and causing the alternator to put out a low voltage? Is there a way to check that separately?

02-21-2016, 10:28 PM	#6
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,322	Re: Alternator Replacement Question I'm replacing my perfectly good alternator for one internally regulated. Unfortunately I'm still using the one I have. Don't know about the wiring, but it doesn't matter anyway, because I'm replacing all that too. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

02-21-2016, 10:39 PM	#7
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Alternator Replacement Question Most auto parts stores can bench-test an alternator. If it's fine, then I'd suspect the regulator. Growing up on the prairies where the next "big town" can be 6 hours away we used to carry spare belts, water pump, regulator, alternator, and fuel pump. Those are the "maintenance" items on a GM of that era. __________________ 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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