Alternater problem? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

80BIG10 · 08-05-2005, 01:00 PM

Hey y'all,

Seem to have a issue with my voltage. While driving my volt gauge is reading just over 13 (which is straight up). Just started yesterday - when I am stopped it drops down to just above the red - maybe slightly in the red. If I put it into park the volts go back up to normal.

Any ideas??

A few months ago I put a new Optima battery in.

If it is the alternater what do you all recomend - brand/amps?

Thanks for any help.

SlickSierra77 · 08-05-2005, 01:07 PM

What size is in there right now? Im runnning a 70 amp with 2 high power amps and have no problem.

80BIG10 · 08-05-2005, 01:34 PM

I am not sure what is in there right now.

I dont have any extra's except a cd head unit. No extra stereo amps or anything.

SlickSierra77 · 08-05-2005, 01:39 PM

Get an Autolite 63 Amp that should work fine for you, they also come with a lifetime warranty.

beaterC10 · 08-05-2005, 01:47 PM

Check the voltage between the alternator output post and chassis ground at idle, it should be around 13-14v. If the voltage is low, the alternator is bad. Next check the voltage between the battery positive terminal and chassis ground at idle, it should be real close to the voltage measured at the alternator. If there is more than 1v difference, the cable is bad.

If the alternator is bad, I would replace it with a new replacement stock part.

a28doc · 08-06-2005, 12:09 AM

easiest way to check to see if alternator is bad is to let truck idle then pull negative battery cable if truck dies then alternator is bad hope this helps Doc

80BIG10 · 08-06-2005, 08:32 AM

Thanks for the help everyone. I am going to try to find time today to check it out.

08-05-2005, 01:00 PM	#1
80BIG10 3 lefts make a right Join Date: Jun 2004 Location: Texas Hill Country Posts: 150	Alternater problem? Hey y'all, Seem to have a issue with my voltage. While driving my volt gauge is reading just over 13 (which is straight up). Just started yesterday - when I am stopped it drops down to just above the red - maybe slightly in the red. If I put it into park the volts go back up to normal. Any ideas?? A few months ago I put a new Optima battery in. If it is the alternater what do you all recomend - brand/amps? Thanks for any help.

08-06-2005, 12:09 AM	#6
a28doc '87 V20 4x4 Join Date: Jun 2004 Location: South Western Ohio Posts: 1,073	easiest way to check to see if alternator is bad is to let truck idle then pull negative battery cable if truck dies then alternator is bad hope this helps Doc __________________ '86 K5 Blazer 4x4 FOR SALE '87 v20 4X4 '99 S10 Blazer 4X4

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08-05-2005, 01:07 PM	#2
SlickSierra77 SlickSierra Join Date: Aug 2005 Location: Keizer,Oregon Posts: 142	What size is in there right now? Im runnning a 70 amp with 2 high power amps and have no problem.

08-05-2005, 01:34 PM	#3
80BIG10 3 lefts make a right Join Date: Jun 2004 Location: Texas Hill Country Posts: 150	I am not sure what is in there right now. I dont have any extra's except a cd head unit. No extra stereo amps or anything.

08-05-2005, 01:39 PM	#4
SlickSierra77 SlickSierra Join Date: Aug 2005 Location: Keizer,Oregon Posts: 142	Get an Autolite 63 Amp that should work fine for you, they also come with a lifetime warranty.

08-05-2005, 01:47 PM	#5
beaterC10 Senior Member Join Date: Jul 2003 Location: Indianapolis, IN Posts: 1,277	Check the voltage between the alternator output post and chassis ground at idle, it should be around 13-14v. If the voltage is low, the alternator is bad. Next check the voltage between the battery positive terminal and chassis ground at idle, it should be real close to the voltage measured at the alternator. If there is more than 1v difference, the cable is bad. If the alternator is bad, I would replace it with a new replacement stock part.

08-06-2005, 08:32 AM	#7
80BIG10 3 lefts make a right Join Date: Jun 2004 Location: Texas Hill Country Posts: 150	Thanks for the help everyone. I am going to try to find time today to check it out.



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