05 yukon xl 1500 4by intermiitant low battery charging

Got an 05 Yukon that's been intermittently charging at 11 some volts for long time. Other day ammeter went halfway down discharge and would not start at the pumps. Got it home, fully charged battery, all connections cleaned, Battery volts go (on my dvm)from 12.45 to 11.6 when started. Even hit alternator with hammer several times! Has anyone out there ever had this problem before? And can alternator be possibly fixed, or has it electronics just gone out . Bout 220k miles on truk. Bought used so not sure bout alt, Thanks for any replies.

JohnandBuddydog said:

Got an 05 Yukon that's been intermittently charging at 11 some volts for long time. Other day ammeter went halfway down discharge and would not start at the pumps. Got it home, fully charged battery, all connections cleaned, Battery volts go (on my dvm)from 12.45 to 11.6 when started. Even hit alternator with hammer several times! Has anyone out there ever had this problem before? And can alternator be possibly fixed, or has it electronics just gone out . Bout 220k miles on truk. Bought used so not sure bout alt, Thanks for any replies.

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Sounds like voltage regulator is done. But to be sure, start engine and measure voltage coming right out of the stud on the back of the alternator at Idle. Stick positive lead on the stud and negative lead on the battery negative. You should see around 13.8v. If you dont then the alternator is done. These series alternators arent easy to rebuild like alternators of the 80's and before. Your alternator actually has the stator leads silver soldered so a regular soldering iron will not do the job for disassembly because it wont get hot enough to melt the silver solder. I would definitely stick your battery on a charger and get it fully charged. Let it rest for a couple hours or so then take a voltage reading off of it. You should see around 12.6v + if the battery is remotely close to being good. Keep in mind just because a battery reads the correct voltage range, doesnt mean it has any kind of in range current output.

I had an issue with my 06 Suburban recently. The voltage would drop a lot after driving for to work, some 9 miles. If I turned on everything electrically voltage would drop to almost 9V! Everything off was barely over 12V. Like 12.3 V.

I replaced the alternator and everything is normal again.

Strangely, I never got a message about charging system on the cluster, but if I unplugged the charger, I did get the message. It was weird, but not sure how that message is activated?