Change In Voltage

brycer867 · November 6, 2011

I have a 08 1500 max 6.0. The voltage in cab has always read around 14 and it would drop and fall as it is supposed to do. I read that they only charge when they need to in order to cut power consumption by not being on load all the time. But yesterday i noticed the gauge way up around 15-16 volts and not dropping at all during a 3 hour trip. I took a meter to the battery at idle and it seems right as it reads 14v. anyone have any ideas why the guage would read so high?

Wires · November 6, 2011

I have a 08 1500 max 6.0. The voltage in cab has always read around 14 and it would drop and fall as it is supposed to do. I read that they only charge when they need to in order to cut power consumption by not being on load all the time. But yesterday i noticed the gauge way up around 15-16 volts and not dropping at all during a 3 hour trip. I took a meter to the battery at idle and it seems right as it reads 14v. anyone have any ideas why the guage would read so high?

I think it just charges when the battery is low. I haven't heard of any GM products being "smart" about charging (if that exists).

If the battery is good, then it should be 12-13V, if it's low, I've had mine charge at 15-16V. When my battery was screwed, it stayed at 15-16V all the time, and would self discharge in about 2 weeks without driving.

My guess is your battery is bad.

wavery · November 6, 2011

Check your battery voltage after the truck sits over night (make sure it is fully charged). If it's below 12.5 in the morning, your battery may be getting weak.

The true test is to have a load test done.

MikeNH · November 6, 2011

I've seen mine run high before but I can't say I've been on many long drives to see if it lasts.

wavery · November 6, 2011

BTW...... If it charged @ 15-16V for 3 hours, it would have boiled most-all the water out of the battery.

Your alternator should be set @ ~ 14.8V.

MikeNH · November 7, 2011

BTW...... If it charged @ 15-16V for 3 hours, it would have boiled most-all the water out of the battery.

Your alternator should be set @ ~ 14.8V.

Not that straightforward anymore. The 900s will vary voltage widely in some sort of routine to charge the battery in a more efficient manner I guess. It isn't load related anymore- I've been going down the road with the highbeams on, heater running full bore and the defrosters running and it'll still keep voltage below 12 on the gauge. Then sometimes with no load at all it'll be past 12. Hard to say for sure where it's running as the gauges on the 900s don't have as many graduations on them though.

brycer867 · November 7, 2011

BTW...... If it charged @ 15-16V for 3 hours, it would have boiled most-all the water out of the battery.

Your alternator should be set @ ~ 14.8V.

Thats what i thought also. The guage is reading higher than what i read with a meter at the battery. I cant find the posts about the 6.0 afm motor having the charging system that starts and stops as required but i know there was one.

wavery · November 7, 2011

Not that straightforward anymore.

"Anymore" has nothing to do with it. 15+V for more than an hour will boil a lead/acid 12V battery. That has never changed.

ifshinxs · November 7, 2011

Mine used to stay at 14-16 V all the time.. I bought the truck used and just thought that was where it ran....That was until I pulled the positive cable off the battery...It was corroded up pretty good.. So I cleaned everything up.. Then I noticed that my Voltage read at 15-16 volts and then dropped to 14 V and now it will drop down to 12-13 V during the day and kick up to 14 at night when I have my lights on..It will also run at 14V after the first start up in the morning after setting all night then drop down to 12-13V after a short period of time.

I had my charging system and battery checked by the dealership..After talking with them and doing some research, I found that a computer controls the voltage needed and adjusts according to load..Now that I'm used to the fluctuation I don't freak out when the voltage drops..

jblakeney · November 7, 2011

Check your battery voltage after the truck sits over night (make sure it is fully charged). If it's below 12.5 in the morning, your battery may be getting weak.

The true test is to have a load test done.

I second this, you don't know jack till you have it tested....... Charging system analyzer will tell the tell. And possibly keep you from making a phone call later.

Jbo

6Sixathome · November 7, 2011

Check your battery voltage after the truck sits over night (make sure it is fully charged). If it's below 12.5 in the morning, your battery may be getting weak.

The true test is to have a load test done.

I second this, you don't know jack till you have it tested....... Charging system analyzer will tell the tell. And possibly keep you from making a phone call later.

Jbo

I had this done the other day at Orielly Auto Parts and my battery voltage was 12.5 and when running was 14.6 ish, the guy said everything looked great.