Thanks guys I did charge the battery out of the truck with a charger with a setting for AGM battery's. I looked at all the cables this morning and it's hard to tell but it looks like there's some corrosion starting in the wire on the ground wire that's bolted to the firewall. I'm thinking I should change the ground wires seeing as that's the one that's been corroded on the battery also. Also I haven't had the battery light on since putting the new alternator in.

 

Well I changed the ground wires this weekend, also added a edge tuner for just the gauges as a friend gave it to me. The volt dropping issue is still there. While driving home after changing the wires they dropped to 13.0 twice. Then this morning I started it with my remote start and when I got into it the volts were bouncing between 12.7 and 12.9 for the first 4-5 miles of my ride into work then they jumped to 13.9-14.2. I did notice when I rolled my window up after getting my coffee the draw from the second or so after the window was all the way up they dropped to 13. Then on my way home they dropped to 12.9-13.1 twice, once when I was pulling into my driveway so when they were at 13 I hit the window switch up and they dropped to 12.6 for a second then jumped to 13.8-14.0 before I shut it off. Sorry for the rant but I'm stumped and about to take it to a shop just would rather save some money and fix it my self.

 

Is the charge / battery light illuminating anymore ?

 

Doesn't this seem like a faulty connection in a wiring harness somewhere? It's really the only thing I can come up with that makes the voltage jump around like this.

- Jack

 

No battery light on that's been off since I put the alternator in.

 

I think you are chasing something you think is a problem, but it is normal operations.

Depending on temperature, previous charge level, battery condition and draw the numbers above are all in the valid normal operating range on a 04+ PCM controlled alternator.
- It is not a constant VDC output.

 

I understand that it's supposed to be in range, what I can't understand is how I would have never noticed the lights dimming before. I have owned the truck since it was new.

 

Watching my scangauge, there is some movement in voltage depending on temperature and electrical load, but it varies from 13.9V (warm days on a long drive with little load)to 14.6V (very cold weather with a lot of load). these swings down below that indicate a shorted battery cell or regulation issue with the alternator. Is there a sense wire that provides feedback to the control system?

 

Hey guys trucks been doing the same voltage bounce between 12.7 to 15.4 when driving, however twice now when it's raining out the volts have dropped to as low as 11. 0 . Even when they drop down to 11. 0 the battery light never comes on. I was taking advice that what they were doing before was normal but I feel like drops down to 11.0 volts are to low. Looking for any advice.

 

If it drops that low, I'd get your battery tested.

 

I'm having just a bit of trouble with this term "bounce". When I hear it (see it), I think of the rhythm you might associate with a basketball, that's being dribbled. Is this what you guys are talking about here? Any fluctuation that's that fast, is most often caused by loose, faulty, corroded connections.

But, if it's a "slow" change, or one that changes rapidly but holds a new high or low value for a longish while (like maybe several hours) then it's often related to the condition of the battery or, some draw on the charging system that occurs now and then. As an example, in my old truck, when I started out on a trip towing our trailer, the voltage would be 14.2V. But, if we stopped someplace for lunch and left the trailer refrigerator on, pulling up to 15 Amps from the trailer batteries, when we'd start driving again the voltage would be between 13.4 and 13.6V, depending on engine speed, brakes being applied, and so on. The alternator was having to recharge THREE batteries, and the large Amperage draw reduced the available voltage. This was a normal condition under the circumstances.

And, I've also noticed that temperature plays a part in this too. In high temps, the voltage is lower than at low temps. This makes sense to me also, since high voltage at high ambient temps would tend to "boil the battery" - something you don't want.

So, it might be helpful to know something about how the voltage "swings".

- Jack

 

Sorry for the term bounce. Usually when it start the truck the volts range from 13.7 to 14.2 they will stay there for a few miles then drop 12.7 to 13.2 and again stay there for a few miles. The couple of times when it was raining they would drop to around 11 and fluctuate up and down for a few miles seeing a high of about 12.5,then after the few miles would go back to the normal 13.7 to 14.2 with some drops to 12.7 to 13.2 for a few miles at a time. I occasionally see jumps up to around 15.4 which don't last more then around a mile or so. I replaced all the ground wires, and checked the positives, just trying to figure this out without having to go to the dealer or a local garage. Thanks for any help.

 

Go over to the parts store and get the battery and alternator tested. It's free, done in the parking lot without removing anything.