Archived Voltage Mystery

[PStraub]

Greetings all.



For the past 2 weeks, my '03 3500 Cummins HO 6speed has had some odd charging issues.



Every once in a while, the system will not charge after start-up, and the voltmeter gauge will shoot down to the bottom (around 8 Volts) and the 'Check Gauges' light will illuminate. Turning off the truck, when this happens (about 1/2 the time now) stopping and restarting the truck sometimes tricks it into charging properly. When it is charging, it charges at about 14. 2 volts.



I've load tested each battery, and they are strong. I've removed the alternator, and installed a spare, and the problem remains the same.



I don't have a code reader, so have been unable to look up or clear any codes.



Any advice?



Peter Straub

 

[JApol]

cycle the key on and off 3 times ending with on. In the odometer area any codes will be displayed. Done will be displayed when all codes have been shown.

 

[LandShark]

It would help us if you filled out a signature to describe your truck (any mods?) and tell us where you are (is it cold there?).

There are two systems on the truck with large electrical loads. The grid heaters are one, but I don't think they could ever draw the power grid down to 8 volts (with decent batteries). The other is the starter and it could cause 8 volts if it was shorted.

Disconnect a wire to each grid heater relay to eliminate that possibility.

If the 8 volt reading is real then all that power has to create heat somewhere. Is the starter hot?

Let us know what you find.

 

[PStraub]

Truck is the '03 3500, HO 5. 9, NV5600, 4x4. Installed a PacBrake in May, otherwise it is stock.

I am located in Calgary, AB. The last two days have been the only time the glow screen has activated that I can remember since last spring.

When the Volt meter reads 8 volts, and I test the batteries in this condition, it shows around 12V or so. I believe the ECM is over-riding the Voltmeter and forcing it to 8V to indicate a problem

Cycling the key shows P2502. I do have an alldatadiy.com subscription, and reading the problem for this says possible causes are:

* Damaged or loose connections in the wiring harness
* Open circuit in the wiring harness
* High resistance in the wiring harness
* Failed generator
* Failed ECM

The first test in alldata says "Using the DRB, check for EVR driver DTC's". What's a DRB and EVR driver? EDIT - never mind... Google answered this for me.

I've already tested the generator by replacing it with a spare, so I'll rule that one out. I guess I need to dig into the wiring and clean that up. Corroded wiring is very likely in this environment. I'll cross my fingers that the ECM itself is not the culprit. I suppose it's possible, as the PacBrake installation required me to touch the ECM.

The problem has become progressively more frequent over the past 2 weeks, so corroded wiring seems like a primary suspect.

I'll let you know.

Peter Straub

 

[PStraub]

I cleaned all the battery terminals and connections. Nothing seemed 'bad', but since doing that, my test drive provided flawless operations for the first time in a few weeks. I think I've got it fixed. Thanks
Peter Straub