Low Voltage

One Short of a Dozen
PowerMaster one wire alternator

No, that isn’t describing the number of decent humans remaining alive in Chicago. That’s how many volts the truck was running on. The truck chewed through batteries like an ex-smoker through Big Red. Since not only the plow but the engine itself requires the charging system be in top notch order, I knew this was one of the first items on my to do list. Follow along and we’ll go through the troubleshooting and remedy of the problem. Yes, I did actually end up fixing something, and screw you for asking. Get me another beer and read on.

Issue: Low Voltage and Dead Battery

Most 12 volt cars and trucks (generally anything newer than the early 60s) want around 13-14 volts, with engine running, to properly charge the battery. On-board generation is usually handled by an alternator these days, and this vehicle is no exception to that.

Troubleshooting Process


Since the electrical is supplied by battery, I checked there first. I knew it went through a few batteries (the previous owner said so and I had no reason to doubt him), so I figured I’d check the batteries and the main cables. After a night on my charger, the battery showed a steady 12v and the battery cables looked okay and seated on the battery.

Something is off...

That is a PowerMaster Alternator. Nice unit. Trouble is, PowerMaster doesn’t make an alternator for the Dodge 318/340/360 line of engines. Someone threw some money at this problem and certainly didn’t fix it. A quick look and I found a previous owner had put some metal in there to get a GM 12SI style alternator to work and fit on this Dodge.

Immediately I figured this was messed up and was gonna be the cause of the issue. I looked at it from the side and the belt seemed to route straight. I measured the pulleys (rule of thumb is about a 3:1 diameter ratio between the crank and alternator pulleys) and they were about right. Also, the strap of metal seems stout enough since the case doesn’t move at all. The truck runs and, when I rev it up, the volts don’t change. All this lead me to believe the swap itself to the GM style alternator was not the cause of the low voltage.

Rule of thumb is about a 3:1 diameter ratio between the crank and alternator pulleys.


I got out my multi-meter (yes, you need one noodle head), started the truck, and checked the BAT terminal on the alternator to the battery ground. This gave me about the same voltage I was seeing across the battery itself – 11 volts.


After running the truck 2 beers worth of time, I noticed something. The charge wire from the alternator to the battery start slouching, like a millenial when they get that first paycheck only to realize Socialism is a failed ideology.

I touched the wire. It was very warm and way more flexible than when cold. Figuring I’d found my issue, I cut some 0 gauge wire to length, crimped on some ends and felt confident I had ‘er licked. I started the truck back up and checked voltage across the battery. 12.1 volts. At that voltage, the truck might not eventually die but the battery isn’t really charging either. When I turned my lights on, the voltage dropped to mid 11s.


I finally decided the test the ground on the alternator. I tested the voltage across just the alternator’s charge bolt to it’s case mounting/ground bolt. Low and behind 14.0 volts. Now I have finally found my issue. Likely time and mother nature had corroded the grounds from the engine back to the battery. This alternator was grounded through the bracket used to mount to it to the block.

I found some more 0 gauge wire, cut it to length, crimped on some ends and bam: 14 volts. Lights on, lights off, plow up, plow down, doesn’t matter. That PowerMaster is now giving me 14.0 in all cases.


Late model Dodge and Jeep alternators are funny beasts. They require 4+ wires and are controlled by the vehicle's computer. The GM/12SI style box retrofitted to this Dodge does not. It simply requires a charge wire back to the battery (in my case, I needed to add a ground as well since the bracket on which it mounts is not providing a strong ground itself).

These are very nice and simple units, and man do I love simple. One wire. Even if you learned Common Core instead of real adult math, you can figure this one out. The original Dodge wiring was stowed out of the way. My fancy new wires hummed along and life was good.

So far: Al: 1. Old Man: 0
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