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

76bonanza · 07-11-2006, 11:22 PM

Now that I have my electric fans in when they are running my volt guage at idle is around 13-14 volts but if I turn on my lights or heater and the fans are on drops to about 12-13 volts at idle. I plan on getting a 100 amp sometime. But am I right to assume if I stay over 12 volts I am not draining my battery at idle correct?

67chevy2wd · 07-11-2006, 11:39 PM

I would say that you are fine but I would be worried about burning up the Alt, I don't know how low you can pull them down before it is a problem. I could be wrong though.

Gordo · 07-12-2006, 08:32 AM

Get your hands on a digital voltmeter, attach it to the batttery posts, take a reading before you start the engine, this will be your "base" voltage. To get an accurate reading of your charging system you need to have a fully charged battery to start with. The voltage reading of a fully charged healthly battery would be 12.5 volts, anything less than that charge the battery first. Start engine, increase rpm between 1000 and 1500 with no load you want to see 14.2 or more but not over 15.1 volts. With all loads on wipers,a/c, blower fan, headlights, etc. Take a voltage reading, you would like to see 13.5 volts, anything under 13 volts the alternator/regulator could be bad or is incorrect size for electrical demand.

**truckdude239** · 07-12-2006, 09:38 AM

if you haven't yet upgraded to an interal voltage reg now might be the time i installed one off an 83 chevy k-10 with 350 it easy to do only took me about 30 mins to do http://67-72chevytrucks.com/vboard/s...d.php?t=119379

more power brighter headlights and more stable

76bonanza · 07-12-2006, 10:23 AM

Yes truckdude I have an internal reg already, plan on putting a 100 amp before I install my amp for stereo I am good at 1500 rpm just drops a little low at idle. And brefly when the fans kick on. I am sure they have a high startup draw.

**VetteVet** · 07-12-2006, 12:57 PM

Quote:

Originally Posted by 76bonanza

Yes truckdude I have an internal reg already, plan on putting a 100 amp before I install my amp for stereo I am good at 1500 rpm just drops a little low at idle. And brefly when the fans kick on. I am sure they have a high startup draw.

Read this before you put the 100 amp in. You might want to go this route.

http://www.chevelles.com/techref/tecref14.html

07-11-2006, 11:22 PM	#1
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	alt volt question Now that I have my electric fans in when they are running my volt guage at idle is around 13-14 volts but if I turn on my lights or heater and the fans are on drops to about 12-13 volts at idle. I plan on getting a 100 amp sometime. But am I right to assume if I stay over 12 volts I am not draining my battery at idle correct? __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

07-11-2006, 11:39 PM	#2
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: alt volt question I would say that you are fine but I would be worried about burning up the Alt, I don't know how low you can pull them down before it is a problem. I could be wrong though. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

07-12-2006, 08:32 AM	#3
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Re: alt volt question Get your hands on a digital voltmeter, attach it to the batttery posts, take a reading before you start the engine, this will be your "base" voltage. To get an accurate reading of your charging system you need to have a fully charged battery to start with. The voltage reading of a fully charged healthly battery would be 12.5 volts, anything less than that charge the battery first. Start engine, increase rpm between 1000 and 1500 with no load you want to see 14.2 or more but not over 15.1 volts. With all loads on wipers,a/c, blower fan, headlights, etc. Take a voltage reading, you would like to see 13.5 volts, anything under 13 volts the alternator/regulator could be bad or is incorrect size for electrical demand. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

07-12-2006, 09:38 AM	#4
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,238	Re: alt volt question if you haven't yet upgraded to an interal voltage reg now might be the time i installed one off an 83 chevy k-10 with 350 it easy to do only took me about 30 mins to do http://67-72chevytrucks.com/vboard/s...d.php?t=119379 more power brighter headlights and more stable __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube Last edited by truckdude239; 07-12-2006 at 09:38 AM.

07-12-2006, 10:23 AM	#5
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: alt volt question Yes truckdude I have an internal reg already, plan on putting a 100 amp before I install my amp for stereo I am good at 1500 rpm just drops a little low at idle. And brefly when the fans kick on. I am sure they have a high startup draw. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO Last edited by 76bonanza; 07-12-2006 at 10:23 AM.



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