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Discussion Starter #1
At idle my voltage is more often than not dropping into the 11s. I've seen it as low as 11.2v before I give it some gas. Other times it will stay rock solid at 14.2/3.

When it's acting up if I give it some gas (2k or higher) it will only climb into the low to mid 13s, never back to the 14.2 it should be floating around.

I've been doing a lot of work to my truck lately.
In March I put in a new load boss 165 amp alternator, big 3 upgrade, and supermod electric fan.

I have an amp powering a 12" sub which I've unhooked.
Cleaned terminals.
Cleaned/sanded down connections going to mega fuse.
Checked all grounds, sanded down and added star washers to the ground packs under the hood.
Replaced mega fuse.
Checked big 3 wiring, all looks good. Grounds and the feed to alternator.

Only thing I haven't replaced recently is the battery. It's 3 to 4 years old and has been through a few rough summers and winters. Could that cause the voltage to act like this? The truck starts without issues.

When everything is working fine I can have everything running including the electric fan and still be floating in the 13s.

Any thoughts on where to go from here?
Any easy tests to narrow down my issue?
I do have my old alternator but would hate to put it back on for no reason.
 

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Discussion Starter #2
After some googling I'm going to try to see if the + or - is having voltage drops between the alternator and battery.
 

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I take it a .7 to 1 V drop from battery to alternator ground is a bad thing?
Doesn't sound good..

If you mean the ground connection from the alternator to the negative post on the battery, I'd consider that excessive. It should be very near zero volts.

I would think you need to take a look at all connections on both ends.
 

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Discussion Starter #5
Doesn't sound good..

If you mean the ground connection from the alternator to the negative post on the battery, I'd consider that excessive. It should be very near zero volts.

I would think you need to take a look at all connections on both ends.
From the negative post to the body of the alternator I was getting that much drop.
I have 4 gauge wire so I ran a piece from the battery to a bolt on the top side of the battery and everything seems much better. Saw 14.4v for the first time in a long time.

I'm not saying it's fixed yet but it would appear I'm headed in the right direction.
 

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Sounds like the battery.

Check the voltage coming off the alternator to be sure its good. Take your truck to Advance Auto or a battery shop and have a load test done on the battery.

Batteries do not last like they use to.......if your battery is near 4 years old, it might be on its way out.

I went through this back last summer too.....it was time for a new battery
 

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..Batteries do not last like they use to.......if your battery is near 4 years old, it might be on its way out.

I went through this back last summer too.....it was time for a new battery
Good point, but he's seeing (or was seeing) far too much drop across the connection from the alternator negative to ground, so that's a separate problem.
A poor connection at one end or both ends, or else a deteriorating cable (copper wire can corrode inside the insulation in some circumstances) is the only thing that can cause that.
 

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Discussion Starter #8
Yeah I'm going to replace the battery. Place in town has a yellow top in stock. If I have time this afternoon I'm also going to check all the grounds going to the engine.
 

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Please do not waste your money on an Optima...........the fail quick. Many members here, too include myself have had nothing but problems with them.

Go to Auto Zone and get a Duralast Gold or Platinum. I have them in all of my trucks and they are reliable as hell.....and have a better warranty.
 

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I don't know why so many people have issues with optima battery's. My first one lasted 14 years. The one in my other car is going on 10 years with no known issues. And my truck seems fine at 3 years so far. I use the yellow top battery's.
 

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Discussion Starter #13
Please do not waste your money on an Optima...........the fail quick. Many members here, too include myself have had nothing but problems with them.

Go to Auto Zone and get a Duralast Gold or Platinum. I have them in all of my trucks and they are reliable as hell.....and have a better warranty.

Nuts. Just saw this. My last battery was a Duralast Gold. I'm sure the issues I was having didn't help it's life any.

With the Optima in and the 4ga wire going directly to an alternator bolt I'm staying right around 14v in all situations.
 
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