Low voltage on start up.

[Captrowdy]

New here, I have a 2019 Ram cummings that has an issue. On starting it drops voltage to 11.2 than take several minutes to bring it back up to 14.2v. And if it takes too long truck goes into battery saver mode. So far the checked.
Batteries load test good.
Voltage meter is good and volt drop is correct.
Still does it with grid heater disconnected.
Starter checks out for amp draw.
Alternator tests good.
Any one got any thoughts?

 

[18CrewDually]

Battery connections cleaned with a battery terminal brush? More than likely one of the if not both have a weak cell. A fully charged resting battery should be 12.6-12.8v. After initial startup it will always read low until the PCM kicks in the alternator after it is done cycling grid heater. That's normal operation.

 

[Captrowdy]

True but all battery stuff and including connection has been tested multiple times. The problem is after about a half mile and voltage has not come up it goes into battery saver mode. Also when a half a mile down road when truck goes into battery saver mode voltage is in 11v. Battery at start up is at 12.7-12.8. Voltage stair steps up not smooth continuous rise.

 

[18CrewDually]

At the very least each battery needs to have a load put on them to test. Static voltage is step 1. Step 2 is a load test, at the very least carbon pile load tester. Electronic testers aren't enough, you need that dynamic load test. If they're original batts I would of replaced them right from the beginning if testing wasn't available. Battery issues are pretty common. I think the starter alone is knocking the snot out of them and that's why it gets thrown into saver mode. Just my opinion and experience with electronically controlled diesels.
Maybe I'm missing something from your diag so far but let us know what you find.
To add, can you record your concern and post a youtube video link?

 

[RC Turner]

One of the old rules about batteries is: If it rests good it might be, if it test bad it is. Don't count on a battery test of any kind to guarantee you have a good battery.

 

[06 Dodge]

True but all battery stuff and including connection has been tested multiple times. The problem is after about a half mile and voltage has not come up it goes into battery saver mode. Also when a half a mile down road when truck goes into battery saver mode voltage is in 11v. Battery at start up is at 12.7-12.8. Voltage stair steps up not smooth continuous rise.

FYI your engine is a 6.7 not the 6.9 you listed

 

[Captrowdy]

Ok so all tests negative for any issues, at this time the issue seems to be when pcm fires up alternater it starts voltage increasing, then at about 11.7-11.9 volts stalls rise, then if it in 30 sec or so if it doesn’t continue to rise voltage we get the battery saver mode. However over time minutes it will finally start to raise voltage to 14.2. Mind boggling! Oh all updates available have been done.

 

[chopperman1]

Another vote for bad battery(s) here. Should not drop to 11v after a start, if that were the case you wouldn't be able to restart after 3 or so starts.

 

[Captrowdy]

Well grid heater normally pulls it down that hard but the problem is the alternator when it kicks in it stalls in 11s on the way up to 14s which if it stalls long enough it goes into battery saver mode.

 

[crash68]

I wonder if there's a problem with the IBS which is on the negative battery terminal. It feedback the battery charge information for the ECM to control the alternator with.

 

[Captrowdy]

Ok now battery ia always at 12.8 in morning and the draw down occurs at start up. Hence grid heater. Issue is it doesn’t back up to 14.2 charge voltage stalls in the 11.7-9 volts. Then over time it gets back up to 14.2.

 

[Captrowdy]

So this started in Aug. truck would go into battery saver mode after start up. 2019 3500 6.7 cummings. In earlier post I covered a lot of this but can’t figure out how to tie them together. So truck on starting 12.7v goes to 11.3v then slowly comes up but will stop like 12.3 wait and then after a bit voltage starts to rise again. If it pauses to long you get battery saver mode. Batteries tested good for times all good. Taken to dodge it was there 4 days. No codes no issues. Grounds checked nothing. Alt check nothing. They recommend replacing batteries not there better price else where. So since batteries tested good again didn’t replace. Ok now batteries at 12.3v at start and drop to 10.9v and battery saver mode after starting most days after starting. Then when warmed up and truck started voltages starts in 11s volt goes up to 14.4 then back and forth to 11v like a ping pong ball for over a min. Intake heater solenoid click on then off then whole time then stops voltage goes 14v and stays there. Ok ok so replaced both battery and holy f#%€£\ same thing!!!! Have appt dec 15th but no codes no warning lights. Help! Wish I could attach videos I have it doing both. I don’t get it!

 

[danielmid]

You replaced both batteries or just one?

 

[Captrowdy]

Both

 

[Jim BB]

sounds like voltage regulator it is internal in the alternator
you have a digital multi meter put it on and check voltage before starting truck then check after starting and monitor !
if that is good like me and most i assume you do not have a load tester so take it some where and have a load put on alternator with multi meter and check and see what it is doing ! i may be way off base but that's what it sounds like to me
keep us informed

 

[06 Dodge]

So this started in Aug. truck would go into battery saver mode after start up. 2019 3500 6.7 cummings. In earlier post I covered a lot of this but can’t figure out how to tie them together. So truck on starting 12.7v goes to 11.3v then slowly comes up but will stop like 12.3 wait and then after a bit voltage starts to rise again. If it pauses to long you get battery saver mode. Batteries tested good for times all good. Taken to dodge it was there 4 days. No codes no issues. Grounds checked nothing. Alt check nothing. They recommend replacing batteries not there better price else where. So since batteries tested good again didn’t replace. Ok now batteries at 12.3v at start and drop to 10.9v and battery saver mode after starting most days after starting. Then when warmed up and truck started voltages starts in 11s volt goes up to 14.4 then back and forth to 11v like a ping pong ball for over a min. Intake heater solenoid click on then off then whole time then stops voltage goes 14v and stays there. Ok ok so replaced both battery and holy f#%€£\ same thing!!!! Have appt dec 15th but no codes no warning lights. Help! Wish I could attach videos I have it doing both. I don’t get it!

When the grid heater comes on (at any temp below 66, it in owners manual) it pulls a lot of power from the charging system, your voltage meter will go down to around 12+/- volts until it goes off and depending on out side air temp it my continue to go off and on for 1-2 minutes. Your volt meter will go down even of the engine goes in high idle at 1000 RPM, its just the way it is...

 

[dieseldave]

What is a grid heater ?

 

[RamCares]

Hey there,

We see that you have received some great advice from your fellow forum members! However, if these suggestions do not address your concern and you decide to visit your dealer, our team would be happy to offer additional assistance throughout that process! We're available via private message.

Callie
Ram Cares

 

[turkeybird56]

I wonder if there's a problem with the IBS which is on the negative battery terminal. It feedback the battery charge information for the ECM to control the alternator with.

My thought: Something not telling the ECM/TIPM system to tell the alternator to set voltage correctly. Loose wire in the TIPM??? Bad ground somewhere? Gotta be something in the circuit: Something just not working correctly and I am not a good enuf mechanic, especially in diesel area to offer much.

GONNA take someone with a lot more smarts than me to help U Internet Guessnosis this one.

 

[turkeybird56]

Another vote for bad battery(s) here. Should not drop to 11v after a start, if that were the case you wouldn't be able to restart after 3 or so starts.

If was an M-60, would be replacing all the 24V system batts in series, LOL. My inane attempt at humor.