Rpm and voltage bouncing at idle

[OneBadBernie]

Brand new 2020 2500 Cummins acting funny again. After a remote start to warm my truck (it's like -17c) I get in and start the thing again, it fires right up no hesitation. I'm sitting their at idle for a bit texting and all of a sudden the thing feels and sounds funny. It's a shame I forgot to take a video but my truck was bouncing from 100-700 rpm and about 1/4 to 1/2 battery charge on the gauges in unison. I throttled it up and it was fine but briefly did it again after a stop over, I noticed it takes a few minutes of driving for my battery to read out at just above half I know that's fairly arbitrary due to ie all being smoke and mirrors now adays.

This truck sat for awhile at the dealer as I haven't even owned it a week and it's got less then 1000km on it. This is the first time I've seen a diesel do this and I don't know what to make of it. Is this possible a bad battery cell combined with the grid heater draw or a symptom of a worse issue? I should add that the truck was warm at the time and the tranny was even heating up.

 

[H3LZSN1P3R]

Brand new 2020 2500 Cummins acting funny again. After a remote start to warm my truck (it's like -17c) I get in and start the thing again, it fires right up no hesitation. I'm sitting their at idle for a bit texting and all of a sudden the thing feels and sounds funny. It's a shame I forgot to take a video but my truck was bouncing from 100-700 rpm and about 1/4 to 1/2 battery charge on the gauges in unison. I throttled it up and it was fine but briefly did it again after a stop over, I noticed it takes a few minutes of driving for my battery to read out at just above half I know that's fairly arbitrary due to ie all being smoke and mirrors now adays.

This truck sat for awhile at the dealer as I haven't even owned it a week and it's got less then 1000km on it. This is the first time I've seen a diesel do this and I don't know what to make of it. Is this possible a bad battery cell combined with the grid heater draw or a symptom of a worse issue? I should add that the truck was warm at the time and the tranny was even heating up.

Thats the grid heater cycling its perfectly normal for a cummins the funny sound would most likely be your exhaust brake kicking in as it should

 

[OneBadBernie]

Thats the grid heater cycling its perfectly normal for a cummins the funny sound would most likely be your exhaust brake kicking in as it should

This is sitting in my driveway though and the coolant is at temp and the tranny was warm. I can see how that would cause a voltage fluctuations however does that explain the idle? It was basically as if the truck was dying then comming back to idle then dying again. And not the high idle it likes to sit at when it's heating the cab

 

[H3LZSN1P3R]

This is sitting in my driveway though and the coolant is at temp and the tranny was warm. I can see how that would cause a voltage fluctuations however does that explain the idle? It was basically as if the truck was dying then comming back to idle then dying again. And not the high idle it likes to sit at when it's heating the cab

Thats still normal as the grid heater goes off the intake air temp not coolant temp even with my dual alternators the idle will take a dive and come back as the grid heater draws massive amps

 

[OneBadBernie]

Thats still normal as the grid heater goes off the intake air temp not coolant temp even with my dual alternators the idle will take a dive and come back as the grid heater draws massive amps

That's pretty messed up because all the welding rigs I've operated for work have been diesels...couple even Cummins...never experienced this with any of them

 

[H3LZSN1P3R]

That's pretty messed up because all the welding rigs I've operated for work have been diesels...couple even Cummins...never experienced this with any of them

Perhaps you should post a video, this may be more than it seems

 

[OneBadBernie]

Perhaps you should post a video, this may be more than it seems

Took one. Didn't capture what I had seen though j did capture what I think is the heater drawing down power and the system upping the idle to 1100 to compensate, I almost wonder if before it was the same thing but with the addition of a really week battery? I'm going to have to keep an eye on it...as long as it doesn't **** the bed Monday morning...

The video I took is to large to attach but if I catch it again I'll record it

 

[H3LZSN1P3R]

Took one. Didn't capture what I had seen though j did capture what I think is the heater drawing down power and the system upping the idle to 1100 to compensate, I almost wonder if before it was the same thing but with the addition of a really week battery? I'm going to have to keep an eye on it...as long as it doesn't **** the bed Monday morning...

The video I took is to large to attach but if I catch it again I'll record it

The truck idles up to 1100 to heat the coolant.... i am still thinking what your seeing is normal and the reason you never noticed it with other cummins trucks you drove is they weren't your truck so you weren't paying attention.... if its cold enough when i start my truck tomorrow ill take a video showing how it should be sounding and working as it cycles

 

[OneBadBernie]

The truck idles up to 1100 to heat the coolant.... i am still thinking what your seeing is normal and the reason you never noticed it with other cummins trucks you drove is they weren't your truck so you weren't paying attention.... if its cold enough when i start my truck tomorrow ill take a video showing how it should be sounding and working as it cycles

Oh what I saw this time was for sure normal. However I never noticed the heater drawing down the battery before. Yes I know the truck goes into high idle to heat the coolant (at about 76c) usually to 1000rpm.

What I saw before was the draw down, albeit more drastic, without the accompanying increase in idle (manual says it will increase in idle Slightly to deal with draw). Which I think resulted in the truck being so starved for power that it wasn't keeping the air warm fast enough and was idling from 200ish rpm up to 800rpm in a few seconds and then quickly starved off again.

Makes me think it's the combination of normal operation and terrible Mopar batteries that were probably mostly sitting dead till I called them about the truck on the 13th.

I do wanna compare though I'd be interested in seeing the normal and I'll be keeping and eye on this, gotta be quicker on the old camera.

 

[OneBadBernie]

Truck hasn't done this since....might have been anomaly, going to keep my eyes peeled though.... having other issues