2002 Dodge Dakota, Dash volt meter spikes intermittently

Maintenance/Repairs
1

This Dakota has the 3.9 with about 240.000 miles.

New battery and Alternator within the last 18 months.

The other day after driving about 12 miles the chime “Check Gauges” come on and I noted that the voltage gauge on the dash was buried at Max.
Pulled over shut off the truck and popped the hood. No visible problems. Got back in, started the engine and the gauge went back to it’s normal position. I had expected to see smoke from the alternator or the battery blown to pieces from the overload.
I also noted that there was no excess heat at the alternator or battery.

I picked up my DVM from the shop to carry along and have driven at least 5 trips over 15 miles since. Today the same problem occurred, but by the time I pulled into a close-by parking lot the meter went back to normal. I checked the voltage at the battery and had 13.25 volts with the engine off and 14.40 volts with the engine running. I drove another 40 miles with no problems.

Tomorrow I plan to run a lead from the battery into the cabin, so I can monitor the voltage quicker if the problem reappears.

Anyone have any ideas .

Yosemite

2

If the voltmeter is reading correctly, I’d suspect a loose or corroded connection at the battery, either end, or a bad cable. The spiking high voltage reading could mean the battery connection is gone and the alternator can then drive the voltage up way above the battery voltage. The battery acts as a voltage limiter.

With the voltmeter connected to the alternator output and engine running, try wiggling the various battery cables.

3

Thanks for the suggestion @BillRussell , I’ll try that tomorrow when it’s light out and a tad warmer. It’s only 12 degrees out now and I don’t want my kahonies frozen.

I never thought of checking the cable connections though I just changed out both cables a couple of months ago. Maybe I didn’t get one tight enough.

Yosemite

4

I agree. If the gauge is correct, you’ve got a bad connection somewhere. However, it could be at the PCM, which contains the voltage regulator circuitry. Also ensure all body grouds, including the PCM, are secure.

5

I’m on board with the loose connection theory as well.

6

I got the truck into the shop today and checked things out.

Everything looked good.

I pulled the cable clamps off the battery and cleaned them. I had replaced the cheap-O stamped post clamps with the old style lead clamps a few months ago. When I did wiggle the cables I found that the negative cable was not snugged down as good as it could be onto the new post clamp. I tightened that down good and am hoping that the problem does not reappear.

I guess I’ll just have to drive it and see.

I will post back in a few days my results.

Yosemite

7

I think that was probably the problem. The voltage regulator isn’t able to properly do its job without it, the alternator, and the battery all sharing the same exact ground reference. B/c there’s so much current travelling about in that circuitry, even a small resistance can cause problems. I’ve had a problem on my Corolla before where everything is fine all summer, then cold weather causes some metal in something to shrink a little I guess, and the battery cables come slightly loose from the posts, and weird electrical problems ensue. Re-tightening fixed it straight-away.

Have you tried installing a temporary wire from the battery to the cab and hook it up to a meter so you can watch it? That’s a very good idea you suggested if the problem returns. Better probably if you can use an analog style meter rather than a digital, so it is easier for you to see if the needle does any untoward jumping around. Best of luck.

8

I did not run a line into the cab, but am planning on doing that tomorrow.

It will give me something to do while I wait for a brake job to show up.

Yosemite

9

I’ll tell you a funny story about running power lines into the truck’s cab. I had run some temporary power wires from the battery area in the engine compartment to my truck’s bed as part of an alarm system I was in the process of installing. Just a test of what I’d installed at that point. The test went ok and I was awaiting some more parts before I did a permanent install so I just left it like that. No worries, right? A few days later I got into my head to drive to the local lumber store and buy a bunch of lumber, a man cannot have too much lumber, that is my personal motto. I do so like the smell of green lumber. Anyway, I buy it and I stack it up about 3 feet high in the truck’s bed there in the parking lot. Pretty big stuff, 14 foot long green douglas fir 2 x 12’s and such. As I was heading back inside the store from the parking lot to buy something I forgot, I looked back at the truck – you know how we truck owners all do this? … lol — and lo and behold clouds of black smoke was billowing from under the lumber! Oh no! It turned out the weight of the lumber had shorted out those alarm wires. I had installed a fuse in the circuit, but the fuse had too high of current limit for the wire size, since I was planning on installing a thicker gauge wire with the actual install, once the parts arrived. Anyway, it was touch and go there for a while, whether I’d get that circuit disconnected before the lumber caught on fire and truck burned up … lol . . it turned out much of the smoke wasn’t the lumber burning, but the insulation on the wire burning . The copper wire got so hot it melted. So if you need to know a way to melt copper, I’m your man.

10

You really don’t have to run a wire into the cab Yosemite. Just tie your meter to one of the fused circuits in the dash fuse panel. The voltage will be slightly lower than at the battery due to wire losses but that is really insignificant for your purpose here. It’s still 12 volt power.

11

I thought of that @Cougar, but then I remembered I have a lighter plug that has leads on it to keep the memory alive on some vehicles. I just used that to hook my meter to.

And @GeorgeSanJose , I can top your story.

Years ago I had built a really nice looking cap for the back of my truck. It was all made of wood and stained and varnished. Two side doors and the entire back door raised to give you a little shelter when working at the back of the truck. If I remember right the outside was covered with that 3/8 thick cedar that you line closets with.
The only reason I gave that one up, was that the next truck box was 3 inches wider that the old one.

I’m sure most of you know that I have shod horses for over 35 years and with that you have a forge in the back. Mine was a coal forge with a 12V blower and when you left one barn…if the forge was still smoldering…that was fine…you’d need it at the next place. As long as the blower was off the forge was cool enough to not harm anything.
This is a common practice with most Farriers that use a coal forge. You just put a little green coal on top and let it smolder. It takes too much time and effort to relight the coal each stop.

I had been traveling down the highway for 20 minutes and came to a stop where I needed to make a left turn. As I made the turn I got a whiff of smoke and thought “that’s just the forge”, then half way through the turn I thought, "that’s not coal…that’s pine!!!

I pulled over as soon as I could. I opened the back door and my forge was belching out flames 2 feet high and one roof support was burnt almost to the 1/4 inch layer that covered the outside of the roof. I had no extinguisher, but my quart water bottle was just enough to soak a towel and pat the burning embers on the roof support out.

I figured that my tool box that is carried to the horse, rolled and somehow turned the knob for the blower.

I thought later, that had I been keeping on the same road and not needed to make that turn…the entire cap could have been engulfed in flames before I noticed it. I’d be wondering why so many people are on this road that know me…they’re all waving!!!

I was lucky and it took little to repair, but I sure learned a lesson.

Ever since, I carry an extinguisher and there is a switch…like a brake light switch… that shuts off all power to the back end as soon as the cap’s rear door is closed.

Yosemite

12

That’s one smokin’ truck ya got there @Yosemite … lol … good story, thanks for sharing :wink: