1993 Dodge Dakota LE, 5.2L, A518 Auto Trans, RWD, 190,000 miles, original owner.

OK HY, here we go again. I fixed that voltage fluctuation awhile back when I discovered the plug going to the voltage regulator was faulty. This was many months ago and since I fixed that the voltage gauge has been rock solid with zero fluctuation. Well now today it's acting up again. Not the same way where the needle on the gauge would go wobbly. It's different now. I'm driving along and the needle is steady as usual. But as I come to a stop, the needle goes down (lower voltage). Then as soon as I hit the gas pedal it goes right back up again and is steady. So basically the voltage goes dpwn at idle and goes right back up the second you put gas to it. I checked all my connections again but not finding anything. Had the wife stare at my gauge while I went out there and wiggled stuff. Nothing.

Any ideas? Fix one problem, get two problems back. Can't win.

 

That's pretty normal. Voltage will fall off as engine RPM goes down. The alternator isn't putting out as much at lower RPM.

 

I did measure the voltage on the battery terminals at idle speed and it was 13.8v. But what has me scratching my head is why all of a sudden has the needle started moving?? These past 10 months or whatever it's been that needle was rock solid, didn't move even in the slightest. Why now?

 

Phase of the moon?

State of battery charge will affect that as well. So long as it is over about 13 volts at idle, (and doesn't go over about 15, ever...) It's all good.

 

It did cross my mind that maybe the battery is going bad?? Or that the truck has been sitting at the repair shop for three weeks waiting for parts?? The battery is 2 years, 9 months from the sticker on it. A Wally World Max Start or whatever they call it. Their top of the line.

 

It should be able to tolerate sitting for a week or three... It might bleed of a bit of voltage, but that'd be about it. My truck has sat for almost a month, and fired right up. I *think* my battery is a bit over two years old..... I think.... But, if the truck starts every time you turn the key, doesn't struggle to roll over, it's all good.

 

Yanked out my battery tester. Here's what I got. Says battery is good, state of health at 78%. It's an 810 CCA batt but says I'm getting 636 CCA. Resistance at 4.59. Seems a little high but not crazy but I'm not sure. Battery is 46 months old. Says to recharge so I have it on a slow 2 amp charge. Seems to me it always says to recharge. I tested my wife's battery. Hers is 5 months older than mine. Same brand. Her SOH is 100% says nothing about recharging. She has a 650 CCA batt and says it's putting out 740 CCA. That's interesting.

 

Get a load tester, Then you will see if it's steady under a load or if the needle starts to drop. I think the volt gauge gets wonky in it's old age. Mine used to stay on 14 just about all year round. Will fluctuate when cold. Now one day it's at 14 the next it reads almost on the 12 line. I know its the gauge because I checked it against my meter.

 

Yeah, I have a tester. Everything checks out. Battery definitely has the edges worn down but it still has life in it according to the tester. It performs perfectly fine. What has me scratching my head is that needle was rock steady and as soon as I fire it up after sitting for three weeks the needle starts dipping at idle. Rises and holds rock steady again once I hit the gas. Hard to believe that is coincidental. Like everything else with a 32 year old truck, ignore it. It'll either go away or explode. If it makes a noise, turn up the radio. In any case there's nothing I can do about it.

Reminds me of a story. A few years ago I was hell bent for election to get rid of every rattle, squeak, rubbing, scraping, and clunking sound from inside the cab. It took a few weeks but I found every single one of them and eliminated all of them (this is a story within itself). It was blissful silence...for about a week. Then one by one they returned. Not even the same sounds. New ones. To hell with it. I gave up. Old trucks are supposed to be noisy.

 

OK HY, I'm as baffled as someone can be. This thread is about my most recent discovery of voltage fluctuation that started up 3 months ago...again.. Two signs that tell me this. One, the dash gauge is bouncy. Two, my lights dim at idle and brighten once I give it a little gas. Clearly the voltage fluctuates. So now about three months after this reappeared (this is not the first time this has happened), I decided to replace everything in my external voltage regulator setup. Everything except the voltage regulator itself and the ground cable going from the regulator to a ground point on the alternator. All new wire, connectors/terminals, wire harnesses, relay, fuse. Presto? No more voltage fluctuation. A human cannot inspect, redo, and test the connections more than I have. To no avail. It takes replacing stuff to fix the problem. I do not know why. Could I just have crappy wire that doesn't stand up to the high engine compartment heat? Don't get it. Next time this happens I think I'll just replace one wire/one component at a time to see if I can isolate the problem. I'm guessing it's the main power wire going from the relay to the regulator. That's been sensitive in the past.

Oh, and my alternator burned up a week ago. Sparks flying out of it and it quit charging. That was an AutoZone rebuild from Mexico. Got a little over 20,000 miles out of it. Total junk. So I put my Wai (Denso) alternator back in. That has less than 5,000 miles on it. Bought it new. That was the one that was in the truck when I had that fire this past summer. It got scorched up a bit but I did a deluxe cleaning before reinstalling it. Works fine. Denso makes good stuff.