06Cummins

I notice it at night...after i start up and begin to drive the batt gauge will go from over 14 down to the very bottom edge of the green(lights will dim) then it will kick back up to over 14 and then back down several times. Whats the deal with this? Is it normal or do I need to take it in?? Thanks, Jason

djgaston

Mine does this as well. After about one minute, it does not happen anymore. I don't know much about diesels, I just figured it took a lot of power to get started and it takes a minute for the alternator to start cranking out some power. I really don't know, but it does happen to me as well.

xyzer

It is the Grid heater. It heats the air before it is compressed in the engine. I believe it is for emmission purposes and to aid in starting in cold weather. Cummins doesn't have "glow plugs". Your voltage gage fluctuation is normal!

Uncle Red

If your lights dim along with the voltage drop and it's a repeating cycle it's probably your grid heater. It will continue to come on and off until the intake manifold reaches a certain temp. not sure what the temp is though.

rammtuff

Or if you drive over a certain speed (20mph I think)

06Cummins

awesome..thanks guys!

underwoodtransp

it will do it untill the incomming air reaches 70* once the turbo warms up it has no problem maintaining this.

The 20mph thing is just because you are working the truch hard enough to warm up the turbo.


Don't worry all of the best trucks do this, It is as common as the shut down squeek. Gotta love it!!

TexasCTD

Yep, once the air temperature warms up in the spring it will stop doing it again until next fall/winter. I think around 60 degrees or so, the grid heaters will stop cycling. Also, once your truck is warmed up it should stop.

WACTD

Completely normal. It's the grid heater, as others have stated. This behavior is even mentioned in the Dodge owner's manual. I originally noticed it because the headlights dim a bit.

Chuckharper

On my 99 3500 I have the same issue, but my question is once you start the truck shouldn't the voltage gauge go to 14 volts, mine will hang around the 8-10 volt mark for a while before it jumps to 14 then drops down then back up and it will bounce back and forth for a minute. Another question is if both batts are weak will it not allow my truck to run properly, sometimes it will run fine other times it will buck n jump like I'm punching the throttle and immediately letting off over n over, I'm really without ideas

Lary Ellis (Top)

No it will NOT immediately go to 14 volts while the grid heaters are cycling...they pull a huge amount of current, more than the alternator can put out which is why they cycle as they do.

What codes is it throwing? that would be the first thing to check on the bucking issue.

Chuckharper

It's not throwing any codes

BarryG

IIRC
grid heaters quantity= 2
grid heaters amp draw 90 x 2 =180
max on time at startup 30 seconds (preheat, wait to start light)
max cycle time 190 seconds
max speed they will cycle 23mph
IAT sensor (intake air temp) is used for temp reading

Joey Bennett

Dodge cuts out alt charging when the intake heater kicks on alt stops changing that’s why it drops so far no other truck does that after replacing both batteries and alt. I can see dropping 2 volts not 6-8 volts l have thought about bypassing something but paying that much for the truck I’ll let it slide for now

Lary Ellis (Top)

Joey, The alte rnator is still charging when the gauge drops...it is just sucking a HUGE amount of amps so it can't keep up. Once it warms up a tad it quits doing that.

Completely normal, not a issue at all