View Full Version : Dodge 3500 Cummins Electrical Problem?

10-12-2009, 08:21 PM
I have the above mentioned vehicle, and I have noticed something funny with the alternator and voltmeter first thing in the morning. When I first start it up, even after waiting for the pre-heat light to go out, the voltage reading is below 14 volts, and the engine runs a little rough. After a few minutes (less time in warmer temperatures) the voltage gauge pops up to over 14 volts and the engine is now fine.
My diesel guy says that this is the effect of some strip heater that goes off after a while. I am wondering if this is true, or my alternator is weak, or both.

10-12-2009, 08:38 PM
Its the grid heater in the intake to preheat the air until the engine warms up some. You can watch the volt meter swing as the grid heater cycles on and off ever few seconds until engine warms up some.

Flying Dutchman
10-12-2009, 08:41 PM
I have a 2008 Ram 2500, and have very similar indications with the voltmeter on engine start, with the exception that I do not have a rough idling engine. Within a minute after start (quicker in warmer temperatures) the voltmeter will increase to 14V and remain there. I have queried the dealer during routine oil/filter servicing and was told the system is operating as designed (no added clarification given). At the time of my inquiry I was concerned that I was experiencing a problem with either the voltage regulator or the alternator. I now believe that it is just functioning normally, however I do make a point of looking at the voltmeter to make sure that it does indeed indicate charging soon after engine start.

10-12-2009, 08:57 PM
The glow plugs on the powerstroke continue to run for up to 2 minutes after starting. Maybe the Cummins does the same as well as the grid heater.

10-12-2009, 09:24 PM
That is normal. I had the same thing and ask the dealer to look at it and they said that happens for the first couple of minutes while it warms up. They found one of my batteries was bad. Mine was also failing to start after sitting in the drive for four or five days. Like you, I thought the alternater was going bad. The two problem were unrelated.

10-12-2009, 09:25 PM
I had a 2006 that did the same thing as you describe including the rough idle and an occasional hard start issue. I did some research on Dodge/Cummins forums and discovered a Technical Service Bulletin from Dodge that addressed the problem with a reflash of the computer. I went to my local Dodge dealer and had to talk and/or convince the service writer to do what I was asking him to do. He checked for the TSB using my VIN and found what I was telling him about. They reflashed the computer with the upgrade and took care of the rough idle/hard start problem and made the electric "surge" somewhat better. If I were you I would ask the service writer to have the reflash covered under the 100,000 mile/5 year engine warranty

I now have a 2009 and it also has an electrical "surge" until the "post-heat cycle intake manifold heater system" stops cycling. The duration of this cycling is controlled by the engine control module. This is covered on page 45 of the "diesel supplement" to the Dodge Ram Owner's Manual.

10-12-2009, 09:37 PM
They ha ve been doing this at least 2004. The colder it is the longer it will take to come back up and if you are using lights etc it will take a little longer.

10-12-2009, 10:31 PM
I had an 01 and the intake heater cycled until warm up or until your speed goes over 25mph. I now have an 08 3500 and nothing has changed. The heater will cycle till warm up or until speed goes over 25mph. I did find out that the heater activates when outside temp goes below 60 deg.
WDK450, You don't have a problem, it's normal.

10-13-2009, 05:02 PM
Or, do a grid heater delete. Eliminates the voltage sag also, the intake flow is greatly improved.

10-13-2009, 06:09 PM
You only want to remove your grid heater if you are never going to park in a cold climate. Any chance of going into cold country in the winter you better leave it in or carry a long cord for the block heater, if you have one.

10-13-2009, 06:21 PM
You would be surprised how well the mightly cummins starts without the heater.