Battery or alternator??????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1986Silverado · 08-10-2004, 07:02 AM

Got in my truck to come home this morning and it would not start. All lights came on and did not seem dim. Left the light on and tried to crank it, lights went out, let off the switch and they came back on. Well got it jump started. I noticed on the drive home the volt guage would be at 13 while moving at about 45mph, but when I slowed down it would gradually go down towards the red line. And at a stop light it was just above the red line. Got it home, shut it off, tried to crank it back up and it turned over really slow and drained almost immediately. Is it the battery or alternator?

GMCLS1 · 08-10-2004, 07:56 AM

Sounds like the alternator.

Grim Reaper · 08-10-2004, 09:05 AM

Good chance both. Battery ate it and burned up the alternator. I would start with the battery and have it tested.

**76sierraclassic** · 08-10-2004, 12:02 PM

Quote:

Originally Posted by Grim Reaper

Good chance both. Battery ate it and burned up the alternator. I would start with the battery and have it tested.

Could be the other way around too. If the alternator bit the dust, you would have been pulling juice directly from the battery and could have cooked it. But I agree with Grim, have the battery checked first. Then, even if you change it and everything seems ok, I'd still have the alternator tested too. Pretty much any auto parts store will check it for free, and they can usually check it while it's still on the truck.

Mike

Russell · 08-10-2004, 12:25 PM

The poor man's way of testing the alternator is to pull the postive battery cable off the truck when it is running, if it dies, the alternator is definitly done, but also check the voltage coming out of the alternator, should be like 14 volts or something.

1986Silverado · 08-10-2004, 04:16 PM

Went outside to work on it and it is completely dead, no lights, nothing. So I put my marine battery in it, fired right up. I pulled the positive battery cable and it died instantly. Gonna pull the alt off and go have it tested tomorrow, no time today.

Russell · 08-10-2004, 04:23 PM

That tells me your alternator is fried, too bad you arn't a bit closer, I have like 4 of them, lol

1986Silverado · 08-10-2004, 04:49 PM

Quote:

Originally Posted by Russell

That tells me your alternator is fried, too bad you arn't a bit closer, I have like 4 of them, lol

Yep, by the way Russell, could you send me a pic to my email of one of those Canadian speedo's? May try one just for looks

Russell · 08-10-2004, 06:14 PM

Quote:

Originally Posted by 1986Silverado

Yep, by the way Russell, could you send me a pic to my email of one of those Canadian speedo's? May try one just for looks

You have mail!

blink32 · 08-10-2004, 11:29 PM

Another easy way to test the alt is with any kind of volt meter. I have a cheap $5 analog unit I use. You just start the vehicle and while its running, put the + of the tester to the + on the alt and the - of the unit to a good engine ground. Meter should read in the 14+ volt range. The exact voltage will be in a manual some where, but other vehicles I have worked on always called for 14.1 - 14.4 volts at the alt when running. If you don't get that voltage then its time for a rebuild or a new one.

1986Silverado · 08-13-2004, 03:30 PM

Turned out it was both, the battery would not hold a full charge and the alternator was not putting out any voltage............replaced both and it fired right up!

Russell · 08-13-2004, 05:10 PM

Good to hear you got her working

SanitysBane · 08-13-2004, 07:40 PM

off topic-russell, looks like you can make some good money selling the canadian clusters to us americans

cliffsta · 08-14-2004, 12:20 AM

yeah my battery is on its last leg. volts fluxuates between 14 and 10, independant of speed.

08-10-2004, 07:02 AM	#1
1986Silverado What I drive Join Date: Apr 2004 Location: Star, MS Posts: 418	Battery or alternator??????? Got in my truck to come home this morning and it would not start. All lights came on and did not seem dim. Left the light on and tried to crank it, lights went out, let off the switch and they came back on. Well got it jump started. I noticed on the drive home the volt guage would be at 13 while moving at about 45mph, but when I slowed down it would gradually go down towards the red line. And at a stop light it was just above the red line. Got it home, shut it off, tried to crank it back up and it turned over really slow and drained almost immediately. Is it the battery or alternator? __________________ 1986 Chevy Crew Cab Dually(Choo-Choo Conversion) 2006 Chevy Equinox

08-10-2004, 07:56 AM	#2
GMCLS1 1987 GMC Sierra Classic Join Date: Feb 2004 Location: South Carolina Posts: 121	Sounds like the alternator. __________________ Gary L Hilton jr

08-10-2004, 09:05 AM	#3
Grim Reaper Registered User Join Date: Jul 2001 Location: Atlanta GA Posts: 1,704	Good chance both. Battery ate it and burned up the alternator. I would start with the battery and have it tested. __________________ Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project

08-10-2004, 12:25 PM	#5
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	The poor man's way of testing the alternator is to pull the postive battery cable off the truck when it is running, if it dies, the alternator is definitly done, but also check the voltage coming out of the alternator, should be like 14 volts or something. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

08-10-2004, 04:16 PM	#6
1986Silverado What I drive Join Date: Apr 2004 Location: Star, MS Posts: 418	Went outside to work on it and it is completely dead, no lights, nothing. So I put my marine battery in it, fired right up. I pulled the positive battery cable and it died instantly. Gonna pull the alt off and go have it tested tomorrow, no time today. __________________ 1986 Chevy Crew Cab Dually(Choo-Choo Conversion) 2006 Chevy Equinox

08-10-2004, 04:23 PM	#7
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	That tells me your alternator is fried, too bad you arn't a bit closer, I have like 4 of them, lol __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

08-10-2004, 11:29 PM	#10
blink32 Registered User Join Date: Dec 2003 Location: OTR Posts: 338	Another easy way to test the alt is with any kind of volt meter. I have a cheap $5 analog unit I use. You just start the vehicle and while its running, put the + of the tester to the + on the alt and the - of the unit to a good engine ground. Meter should read in the 14+ volt range. The exact voltage will be in a manual some where, but other vehicles I have worked on always called for 14.1 - 14.4 volts at the alt when running. If you don't get that voltage then its time for a rebuild or a new one.

08-13-2004, 03:30 PM	#11
1986Silverado What I drive Join Date: Apr 2004 Location: Star, MS Posts: 418	Turned out it was both, the battery would not hold a full charge and the alternator was not putting out any voltage............replaced both and it fired right up! __________________ 1986 Chevy Crew Cab Dually(Choo-Choo Conversion) 2006 Chevy Equinox

08-13-2004, 05:10 PM	#12
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Good to hear you got her working __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

08-13-2004, 07:40 PM	#13
SanitysBane Registered User Join Date: May 2004 Location: Lubbock, Texas Posts: 2,121	off topic-russell, looks like you can make some good money selling the canadian clusters to us americans __________________ '96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer

08-14-2004, 12:20 AM	#14
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	yeah my battery is on its last leg. volts fluxuates between 14 and 10, independant of speed. __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

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