2012 HD2500 work truck alternator voltage too high?

[ifixedit]

Hello all,

 

It's been a while since I've visited or posted here and I'm hoping someone can help solve a mystery. 

 

I picked up a nice clean 2012 'plain Jane' 2WD regular cab HD2500 work truck with the 6.0 'G' vin code (no AFM) last summer.  An issue as of late is it seems the alternator is over charging nearly all of the time.  When I first start the truck it will immediately jump to 15+ volts and go as high as 15.25  or so and will then settle down some to around 14.8+ volts and never goes any lower but it will still all of a sudden just spike to over 15 volts while I'm driving or sitting idling.  I noticed this recently during the day (in cooler weather).  I verified the daytime headlights are working which puts some load on the system but it will still often jump to over 15 volts and again never goes below about 14.8.  If I turn the headlights on (which also turns the tail lights on), and load the system down some the voltage then drops to around 14.3 / 14.4 volts and will stay there, turning the fan to high along with the lights on doesn't seem to do much more to lower the voltage and it still stays around 14.3 or so which seems normal but it never goes below 14 volts, but as soon as I turn the headlights off it jumps right back up to nearly or over 15+ volts.

 

I've done some research and this particular year is supposed to have a voltage sensor on the negative cable which communicates with the computer to tell the regulator how much to charge.  This particular truck does not have one on the negative cable.  Further research shows a voltage sensor for this year of truck but all seem to be only for the 1500's and not for the HD2500.  What I'm wondering is if anyone can confirm for sure if there is supposed to be a voltage sensor on the negative cable of the HD2500 or not, or if the previous owner possibly removed it for some reason?  I though it might be the battery, however the battery is nearly new and load tests perfectly and is not losing it's charge.  I've also cleaned up all the grounds going to the engine and including the one on the frame under the drivers side door.  The only other idea I currently have is the regulator on the alternator is bad.  My concern is if this keeps up I'm going to cook the battery.  Any advice would be greatly appreciated.  

 

Thanks,

 

Marc

[richard wysong]

What are you using to measure the voltage? 14.8 is fine, sounds like the regulator may be a tad on the high side but not enough to worry about

[ifixedit]

Thanks for the reply, Richard.

 

Besides the gauge on the dash being way over 14 volts most of the time I've measured the voltage with the load tester, a multi meter and a scanner, all show the same.  To me when the headlights are off, especially after driving it for a half hour or more there seems to be no reason it would suddenly need to jump to 15.25 volts and stay there.  Which again brings up the question should the truck have a voltage sensor on the negative battery cable?

 

Just for the fun and to make a comparison I hooked up the scanner to my 2023 Z71 crew cab this morning and watched the voltage from start all the way to work which is about a half hour.  Yes, it did at very first just go over 15 volts but then settled to a consistent 14.3 the rest of the trip and never moved.

 

Marc