Electrical/alternator question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Lippyp · 01-22-2003, 08:58 AM

The previous owner of my truck fitted an aftermarket voltmeter as the stock ammeter in the dash is dead. I looked at it today and I seem to be getting about 14/15 volts showing. Is this normal or is it too high? I have a multimeter that I can check the real output to eliminate the gauge being inaccurate (it is a cheapo gauge) where should I test this (across which wires, at alternator or voltage regulator?) Is it likely to be the voltage regulator on the way out as I still have the original setup or is it likely to need the points adjusting or cleaning? I've always been a bit vague on the charging system side of things!

All help appreciated.

MellowYellow70 · 01-22-2003, 10:01 AM

Measure at the battery posts and then measure on the acc terminal in the fuse panel. If both of these readings are +/- .3 volts of the gauge reading I wouldn't worry about it.

barn9 · 01-22-2003, 11:39 AM

From what I've been told, 14/15 is what it should be. That doesn't mean I'm right, it's just what someone told me a few years ago.

shadetree · 01-22-2003, 11:50 AM

Later alternators are designed to charge @ "14-ish" volts. Newer style batteries are also designed to operate in this (14 volt) range. All "12 volt" accessories (lights, radios, starters, ect.) will work with this higher voltage.

Gordo · 01-22-2003, 05:32 PM

14.2 Volts accross the batt posts while the engine is running is ideal for general driving. 13.8 Volts is better for over the road vehicles. 12.6 Volts at the batt posts with engine off is a fully charged batt.

Lippyp · 01-23-2003, 06:12 AM

Sounds like I'm in the right ball park, my battery was nearly flat after not using the truck for about three weeks over the Christmas/new year period (had some snow and way too much salt on the roads!) I charged it up for about 36 hours (I have the smallest battery charger you've ever seen, bought way back when I had a 1200cc Triumph Spitfire!) so it may have been sucking up some power to charge.

I think the battery may well be goosed as this is not the first time it has flattened. The previous owner had only done 50 miles in the year before i bought it so it may well have been allowed to flatten right off.

What specs would you reccomend for a new battery, at the moment it has an 80ah.700 cranking amps battery on it. This is the biggest capacity battery I can get over here in this size casing so if the reccomendation is bigger I'm gonna have to go to a specialist or maybe an Optima gel battery.

01-22-2003, 08:58 AM	#1
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	Electrical/alternator question The previous owner of my truck fitted an aftermarket voltmeter as the stock ammeter in the dash is dead. I looked at it today and I seem to be getting about 14/15 volts showing. Is this normal or is it too high? I have a multimeter that I can check the real output to eliminate the gauge being inaccurate (it is a cheapo gauge) where should I test this (across which wires, at alternator or voltage regulator?) Is it likely to be the voltage regulator on the way out as I still have the original setup or is it likely to need the points adjusting or cleaning? I've always been a bit vague on the charging system side of things! All help appreciated. __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission Last edited by Lippyp; 01-22-2003 at 09:03 AM.

01-22-2003, 10:01 AM	#2
MellowYellow70 Registered User Join Date: Sep 2000 Location: Gower, MO. Posts: 222	123 Measure at the battery posts and then measure on the acc terminal in the fuse panel. If both of these readings are +/- .3 volts of the gauge reading I wouldn't worry about it. __________________ If patience is truely a virtue, Then I am so screwed 1970 Chevy SWB 331 sbc and all the goodies. Under resurection 2001 Vette

01-22-2003, 11:39 AM	#3
barn9 Half a bubble off! Join Date: Jun 2000 Location: Winfield, Ks, USA Posts: 5,588	From what I've been told, 14/15 is what it should be. That doesn't mean I'm right, it's just what someone told me a few years ago. __________________ Just call me LB. '71 Cheyenne, 402BB, hauls blondes, brunettes, or redheads.

01-22-2003, 11:50 AM	#4
shadetree Senior Member Join Date: Dec 1999 Location: Knightstown, in, usa Posts: 2,525	Later alternators are designed to charge @ "14-ish" volts. Newer style batteries are also designed to operate in this (14 volt) range. All "12 volt" accessories (lights, radios, starters, ect.) will work with this higher voltage. __________________ 1970 long fleet, 355 4 speed, primer, walnut goodies

01-22-2003, 05:32 PM	#5
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	14.2 Volts accross the batt posts while the engine is running is ideal for general driving. 13.8 Volts is better for over the road vehicles. 12.6 Volts at the batt posts with engine off is a fully charged batt. __________________ 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.

01-23-2003, 06:12 AM	#6
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	Sounds like I'm in the right ball park, my battery was nearly flat after not using the truck for about three weeks over the Christmas/new year period (had some snow and way too much salt on the roads!) I charged it up for about 36 hours (I have the smallest battery charger you've ever seen, bought way back when I had a 1200cc Triumph Spitfire!) so it may have been sucking up some power to charge. I think the battery may well be goosed as this is not the first time it has flattened. The previous owner had only done 50 miles in the year before i bought it so it may well have been allowed to flatten right off. What specs would you reccomend for a new battery, at the moment it has an 80ah.700 cranking amps battery on it. This is the biggest capacity battery I can get over here in this size casing so if the reccomendation is bigger I'm gonna have to go to a specialist or maybe an Optima gel battery. __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission



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