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Charging Voltage

CtChevy427

CtChevy427

Still Kicking....
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What should the charging voltage be at idle if I measure it with a meter at the battery?
 
Generally 13.5v. Some systems 2005+ kick the generator out at times to save fuel.
 
WarWagon said:
Generally 13.5v. Some systems 2005+ kick the generator out at times to save fuel.
Click to expand...
That feature is for gassers only, the diesel alternator should hold 13.5-13.8 HOT. When it is cold, it will go as high as 15.8 depending on temp. My AD244 will hit almost 16 volts if it's below 40 outside. Found this out the hard way as RV fridges are not happy with anything over 15 volts. Had to figure out what that annoying error message was it would flash out on a cold morning when I would start the truck up. I know mine will RARELY drop below 14.2 even with both airs on and the headlights at idle.
 
The reason I ask is the other day I got the message that it was not charging. Before I could look at the gauge the message went off. I never really paid much attention to the gauge but it seems to take its sweet time to get to the 14V mark even when the truck is hot.
 
As many miles as you have, your brushes may simply be getting near the end of the line. When the brushes get worn, it isn't uncommon for the alternator to randomnly drop out and come back in. As t othe slow to come up to voltage, this is normal. The AD alternators used what was refferred to as a soft regulator. It was setup to slowly come up to voltage on startup so as to not shock the batteries with voltage.
 
Wouldn't hurt to check the usual suspects of bad grounds and loose or broken battery cables and/or charge wire off alternator.

As we cook batteries off out here every 2 years testing them separately is always part of troubleshooting.

Bad wiring via worn insulation is always possible - however this step would be after a physical inspection for worn or sticking brushes as suggested above. And the oddball, yet common to GM, ignition switch failure is possible that will cause all kinds of ghost codes and errors. Check ECM voltage for being low on a scanner is one way to test.

Again I would disassemble the old alternator to be sure it's your issue as intermittent things are the hardest to diagnose and with poor replacement part quality you just can't replace an alternator and give it a free pass when the problem continues.
 
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