Alternator charging issues

[puckhead]

No doubt! I would like to get one. Wish I knew more back when I spent $100 on a Bluetooth OBDII reader. I could have spend that towards a Tech2.

 

[Eriebronze]

I have a 2011 Tahoe Lt z71 and mine just started doing this. Changed out the original alternator, thinking it was going bad and ever since, my gauge does that same thing. A check with a multi meter at the battery tells me it is definitely below full charged at 12.2v and goes as high as 14.8 never heard of this before reading it here. When did they make the change to do this as my 2000 Silverado always stayed right at 14 as did my Tahoe till a month ago.

 

[swathdiver]

I have a 2011 Tahoe Lt z71 and mine just started doing this. Changed out the original alternator, thinking it was going bad and ever since, my gauge does that same thing. A check with a multi meter at the battery tells me it is definitely below full charged at 12.2v and goes as high as 14.8 never heard of this before reading it here. When did they make the change to do this as my 2000 Silverado always stayed right at 14 as did my Tahoe till a month ago.

Welcome to the forum Herb. GM introduced this in the 2000s on different models. I had a 2006 Pontiac with it, drove me crazy until I learned about what it was. GM put it on these GMT900s from the start in 2007. It does help with fuel economy (miniscule) but it is better at prolonging the life of the battery and alternator. Look up the terms RVC and EPM and learn about the technology. You can disconnect it and have the alternator charge at 13.6V by disconnecting the plug on the ring that goes around the negative battery terminal right off the battery.

 

[Eriebronze]

Thanks for the info. what gets me was at times it sets right at 14 all day long. The one post said it will maintain a set voltage in tow haul mode but mine dropped 3 times in tow haul the other day. i would shut it off and restart it to get it back to charging. once mine goes down, it does not go back up unless engine restarted. Wonder if I have another issue.

 

[swathdiver]

Thanks for the info. what gets me was at times it sets right at 14 all day long. The one post said it will maintain a set voltage in tow haul mode but mine dropped 3 times in tow haul the other day. i would shut it off and restart it to get it back to charging. once mine goes down, it does not go back up unless engine restarted. Wonder if I have another issue.

If the battery is at the state of charger the computer wants it to be at it's going to be on the low side until the computer decides otherwise. You can turn the lights on but it will eventually go back down. Read up on RVC and EPM to understand why, when and for how long it works.

 

[gpracer1]

It’s actually mind boggling how complicated and how much computer code and charging strategy algorithms that are used.

In a nutshell the computer (BCM) is controlling the alternator to provide enough power to run the truck and any power accessories while simultaneously maintaining the batteries health by not overcharging in these high under hood temps while also deciding when to throttle back power output to enhance fuel mileage.

Just looking at my Tech 2 under charging info, it monitors and I can view live....

Battery current
Battery sulfation mode
Battery voltage
Batt low at start
Batt open ckt. Tested
Batt open ckt. Voltage
Batt voltage high res.
Idle boost level 2 count
Idle boost level 3 count
Desired battery voltage
Estimated battery temp
Fuel economy mode
Parasitic current
Previous state of charge
Regulator set point
Start up state of charge
State of charge
State of charge low

To see if it’s working you can go into electric power management and play with the generator regulator output and increase or decrease the output and watch the needle move on the dash.

Wish I had this Tech 2 20 years ago!!!!!