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Discussion Starter · #1 ·
Im at my witts end I have searched the web called the dealer and I am finding out two different stories. Can anyone tell me where to find the voltage regulator on my 08 2500 megacab 6.7 cummins. Please help thanks and godbless
 

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Correct me if I'm wrong, but if your taking about the voltage regulator for the alternator, then the voltage regulator is in it.

Sent from my PC36100 using AutoGuide.Com Free App
 

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Dodge uses the PCM to control the alternator, no regulator.

Cory
 

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Discussion Starter · #5 ·
Ok so which would cause my head lights and dash lights to flicker while driving would it be the pcm or the alternator. Im very confused at where I should start to fix my issue. Thanks so far for all the help though
 

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Ok so which would cause my head lights and dash lights to flicker while driving would it be the pcm or the alternator. Im very confused at where I should start to fix my issue. Thanks so far for all the help though
How old are the batteries? You could have them load tested at a auto parts store. A bad battery could cause some screwy things to happen. Could also be a bad ground.

Cory
 

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Ok so which would cause my head lights and dash lights to flicker while driving would it be the pcm or the alternator. Im very confused at where I should start to fix my issue. Thanks so far for all the help though
I assume when you say "while driving" it is more than a minute after starting. Just after starting, the grid heater will cycle on/off making the lights go dim/bright. This usually stops after about a minute, or reaching 20 mph, whichever is first.

My first guess would be bad wiring somewhere. Bad ground, bad battery connection, bad connection into the fuse box under hood, bad connection to alternator. By bad, I mean loose. The voltage regulation is done by the pcm, and they rarely go bad. 2nd choice would be alternator. How many miles do you have? Unlikely third choice is batteries. If your batteries were bad, you'd be complaining about no start or screwy codes after start.
 

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Discussion Starter · #8 ·
Ok well I had one had one battery gobad so I replaced it. I have 105000 mils on my pickup so I guess I will have to start looking at elec. But I wonder if I shouldnt replace the other battery to help. I will go off this for now and get back to you all when im done with that. Thank again for alk the help.
 

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Ok well I had one had one battery gobad so I replaced it. I have 105000 mils on my pickup so I guess I will have to start looking at elec. But I wonder if I shouldnt replace the other battery to help. I will go off this for now and get back to you all when im done with that. Thank again for alk the help.
If you only replaced one battery its possible you still have a bad/weak battery. It's always best to replace both batteries at the same time. I would have them both load tested and check all connections.

Good Luck!
Cory
 

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If it is cool outside the grid heater will cause this you will also see a load on the alt change this is normal also check the batterys one at a time disconected from the truck
 

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I know this is an old thread but I didnt want to start a new thread with a simaler question... So from from what I'm gathering from info I see here is that I don't need to be concerned that my headlights go from normal to dim every couple seconds on a colder morning start? I notice it most on high idle for the first couple minutes but then it seems to go away, my volt gauge moves everytime it dims and this is because the grid heater is cycling on and off? Am I correct? Will plugging in my truck eliminate this on a cold start up?
 

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I know this is an old thread but I didnt want to start a new thread with a simaler question... So from from what I'm gathering from info I see here is that I don't need to be concerned that my headlights go from normal to dim every couple seconds on a colder morning start? I notice it most on high idle for the first couple minutes but then it seems to go away, my volt gauge moves everytime it dims and this is because the grid heater is cycling on and off? Am I correct? Will plugging in my truck eliminate this on a cold start up?
It is indeed your grid heater cycling. Totally normal. Plugging your truck in will not stop it. Again, it's normal. Nothing to worry about. Be worried if it stops doing it.
 

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i have had the same issue with my truck and im completely lost...new batteries, alternator tests good, but after 10-15 minutes of driving it will start to surge, the voltage will jump between 13 and 15 volts, makes it look like im flashing my headlights everywhere i go, it does it consistently regardless of weather conditions, doesnt matter what position the throttle is in, could there be an issue with the grid heater trying to kick on and, for lack of a better term, it being confused...again im lost on this one, i appreciate an help i can get
 

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It is unlikely that the grid heater is coming on after 10-15 min of driving. You could disconnect a wire from the grid heater relay to make sure.

More likely you have a bad/loose battery cable, ground, charging wire to alternator. Inspect/tighten/clean all.

Alternator may test good, but it is difficult to duplicate 10-15 minutes of driving on a battery tester in the store (heat/vibration,...) I wouldn't rule out the alternator yet.
 

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I agree with 2000, your alternator might show up some good results but can't really test the actual driving condition, pretty sure a alternator test won't tell you if you have a bad VR
 

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I agree with 2000, your alternator might show up some good results but can't really test the actual driving condition, pretty sure a alternator test won't tell you if you have a bad VR
Especially on Dodge where there is no VR in the alternator. The PCM is doing the voltage regulation function by pulse width modifying the field voltage to the alternator and monitoring resulting system voltage.
 
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