Charging Voltage

[DBurdett]

My vehicle voltmeter always registers about 15. 5 volts, even during a long drive.

My original batteries did not hold their charge, so I recently replaced them with two new AGM batteries.

The new batteries are fully charged, but the vehicle still continues to register 15. 2 volts at idle even after a long drive.

The dealer technician informed me that he had cleared a code indicating I had a high battery voltage code.



Could this be a regulator problem, and is the regulator part of the alternator?



Any suggestions would be appreciated.

 

[rbattelle]

Usually if it's a regulator problem the charging voltage will increase with RPM. 15. 5 or 15. 2 is a little high, but not so high as I would expect with a faulty regulator. Has your check engine light been on?

Yes, the regulator is integral with the alternator. You could simply remove the alternator and take it somewhere to have it tested. I think Autozone does this for free.

-Ryan

 

[Prairie Dog]

Check the voltage at the battery's with a digital multimeter while the eng is running. If it really is that high then there's a problem.

 

[ata]

Your voltage regulator is in the PCM. The PCM was set to charge WET CELL batteries. Now you have put AGM DRY CELL batteries in the truck and the PCM is not seeing the reading's it was set to and thinking that the batteries are low in voltage. When you buy a battery charger it has a mode switch for Wet Cell and AGM because they charge at different rates. For some reason OPTIMA batteries work better but will still have a higher charge rate.

 

[rbattelle]

Your voltage regulator is in the PCM.

You're right, my mistake. The voltage regulator is in the PCM if you have an automatic, the ECM if you have a manual.



If the regulator is bad, you'll need a new PCM (or ECM).



Prarie has a good idea - check voltage at the batteries. That will tell you whether the gauge in the dash is reading correctly.



I still don't suspect a bad voltage regulator, though, because like I said when left unregulated the alternator voltage scales with rotational speed.



-Ryan

 

[JMarketos]

I'm not speaking first-hand here, just repeating what I have read on here in the past.
(I didn't see what year & model is OP's vehicle... )

For many of our trucks, I have read the in-dash Voltmeter reading doesn't have anything much to do with the actual system Voltage. Rather, the VM displays what the ECM tells it to display. (such as, so the driver doesn't see the Voltage sag way down when the grid heaters are on, even though that's exactly what's happening... ) I've also read that the ECM varies the charging Voltage dependent on other things, one of those being outside temp (I think it raises the charging Voltage when the outside temp gets colder).

I agree with Prarie Dog- check the actual Voltage at the batteries or somewhere in the system with a real Volt meter. It may just be that you have a dash gauge pointer that's not "right on". I found at Wal Mart a few years ago, a digital Voltmeter that plugs into the cigarette lighter. They were less than $20, and often hung on display near the replacement battery rack. I've bought a few of them over time- handy to use as a diagnostic tool. One also resides full time in the cigarette lighter of my truck, for this exact reason. Good luck!

 

[rbattelle]

For many of our trucks, I have read the in-dash Voltmeter reading doesn't have anything much to do with the actual system Voltage.

I respectfully disagree. In my opinion, the dash voltmeter is an accurate representation of charging system voltage except while the grid heaters are cycling. At least, it was up through 2004.



-Ryan

 

[cerberusiam]

The voltage regulator is in the PCM if you have an automatic, the ECM if you have a manual.

Hmmmmm... . but what if you don't HAVE a PCM like the bulk of the 3rd gens?



Pretty sure the charge controls are part of the engine controls becuase it is so critical to engine operation on the CR's.

I respectfully disagree. In my opinion, the dash voltmeter is an accurate representation of charging system voltage except while the grid heaters are cycling. At least, it was up through 2004.

It may be representative of charge, discharge, and load but not for actual charge in the system. Anything that has a cluster controller, which am pretty sure all the 3rd gens do, all the gauges are doing is mimicing what the controller is telling them via the ECU. That gauge won't tell you when you have a bad battery and the system is over charging, one usuals finds out when the battery blows up.

 

[Prairie Dog]

Ever notice how the VM dosen't swing with the grid heaters? At east that part of its operation is just a show.
OTOH, when my battery's were going bad they would cause the VM to dip like the grids cycling except it did it about 3x faster. New battery's solved the problem.

 

[rbattelle]

Hmmmmm... . but what if you don't HAVE a PCM like the bulk of the 3rd gens?



Pretty sure the charge controls are part of the engine controls becuase it is so critical to engine operation on the CR's.

You know, I think I'm having a bad week. I must be, because this is twice now I've consulted the service manual and misread it.



You are correct - the voltage regulator is in the ECM for all diesel engines. Here's the relevant passage from the service manual:

The Electronic Voltage Regulator (EVR) is not a

separate component. It is actually a voltage regulating

circuit located within the PCM (Powertrain Control

Module) (within the ECM for diesel engines). The

EVR is not serviced separately. If replacement is necessary,

the PCM must be replaced.

Here's what it says about the voltage gauge:

System Voltage Message - Each time the cluster

receives a system voltage message from the PCM

or ECM indicating the system voltage is between

about 9. 5 volts and about 15 volts, the gauge needle

is moved to the relative voltage position on the gauge

scale.

There's a separate section somewhere that says the needle movement on diesels is supressed while the grid heaters cycle. As far as I know, 2nd gen trucks don't have the needle suppression and Dodge added it for the 3rd generation to cut down on service calls for faulty charging systems during cold weather.



-Ryan

 

[Prairie Dog]

It didn't help though Ryan. My buddy bought a new truck in 06 and the first time he saw his dash lights rhythmically dimming, he called the dealer who told him the alt was probably bad and to "bring it in, we'll fix it rite up!".
Then he called me.

Scotty

 

[rbattelle]

It didn't help though Ryan.

Well, let's be honest - there are lots of threads started by people worried that something is terribly wrong with their electrical system. They usually cite the rhythmic dimming of all the lights and the low charging voltage.

Frankly, short of providing a reminder monkey with every truck I don't think there's any way for Dodge to avoid service calls like that.

It would be nice if the salesmen knew enough to explain carefully to each customer that it's normal behavior in winter. You can imagine unscrupulous businesses charging a fortune to "fix" the problem.

-Ryan