'86 Samurai alternator voltage too high

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AZjeff

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I've had a couple of no-starts with the Samurai in the past month, after starting it and driving somewhere in town. When it wouldn't start the dash lights would dim and it made no starter noise. Luckily I could bump start it and get home. I thought it could be because it's only run on weekends and maybe only a few miles. It wouldn't start yesterday afternoon so I put the charger on it and it went to full charge in a couple of hours. Measured 15.09 volts on the battery after taking the charger off and 15.05 this morning. Out of curiosity I measured the voltage of the alternator and at idle it's putting out almost 16 volts and at 2500 rpm 18 volts. The battery is just over a year old, a NAPA. All cells show equal acid near the top. Apparently the voltage regulator has gone bad? I confirmed voltage against my Solar charger, it's .2v different. Electrical is not my thing, any help is appreciated. Can something outside the alternator cause the high voltage?
 
I think you have it. Regulator in the alternator is bad causing too high of voltage, Plenty of youtube videos on how to change them vs buying a new alternater.
 
Zuk in the wilds, we just got back from hiking to the top of that rocky little mesa in the background to see some ruins. The old girl still gets around pretty well. (I meant the Zuk.)
 
I love seeing older cars like that still being used. Like an old hunting dog, the owner never let’s go of the old faithfal.
 
Over charging a battery releases H2, A spark can blow the top of the battery off. AMHIK Fill the battery when the level drops. I wouldn't drive it much until it is fixed.
 
Also, please, please add a good new ground from the negative post of the battery to the alternator mount, or somewhere close. The alternator must see a real "0" to know what it is supposed to do ...

One of the problems of all aging equipment is the ground side. On the Pos side it has voltage to move things. On the ground side it has no voltage, but still must move the same current back to source. As time goes by and water does its thing, all those old connections on the ground side build up slight corrosion which makes each a semi-conductor. Then the current that must flow home will develop enough "voltage" to get the current through the connection. The added resistance means that things like the voltage regulator will not see battery negative as zero. They may see ground as a volt or two higher. This can lead to strange situations ...

The new grounds need to be crimped and soldered which will prevent future crevice corrosion. I use at least #8 AGW stranded wire. On older vehicles I always add one from the engine to the firewall to help with gauges and such. One from the bat neg ( - ) to the radiator support so the lights are brighter. And for sure, one to the alternator. Puts the whole system on an even reliable ground. Amazing how much better things run
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The big battery neg cable was almost always just crimped and it has developed "crevice corrosion" in the years it's been on the road. And it's never been cleaned and lubed on the connection to the block ... So even if you clean the bolt and the cable eye, it will still be slightly off. The new added grounds will help. The big cable can take the starter load, but the new cables will take the running loads and keep everything nice and equal
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You have also likely boiled your battery to death. I know you say the water level's fine but with it not starting...

Since the alternator is in runaway the battery is the only thing keeping voltage levels remotely sane by soaking up as much as it can. A sucky battery can kill a new alternator.

While you have it where you have it now, run it and put a voltmeter between the alt case/ bracket and battery negative terminal. Should be < 0.1 volts and ideally zero. Do the same with the big lug post and battery positive. You should clean the whole basic set of terminals up anyway but if you find something here more digging will be required.
 
I'm just going to commend you on keeping a Samurai alive for over thirty years. They were excellent off-road vehicles, but they didn't exactly have a history of being reliable and long-lasting.
 
Originally Posted By: BrocLuno
Also, please, please add a good new ground from the negative post of the battery to the alternator mount, or somewhere close. The alternator must see a real "0" to know what it is supposed to do ...

One of the problems of all aging equipment is the ground side. On the Pos side it has voltage to move things. On the ground side it has no voltage, but still must move the same current back to source. As time goes by and water does its thing, all those old connections on the ground side build up slight corrosion which makes each a semi-conductor. Then the current that must flow home will develop enough "voltage" to get the current through the connection. The added resistance means that things like the voltage regulator will not see battery negative as zero. They may see ground as a volt or two higher. This can lead to strange situations ...

The new grounds need to be crimped and soldered which will prevent future crevice corrosion. I use at least #8 AGW stranded wire. On older vehicles I always add one from the engine to the firewall to help with gauges and such. One from the bat neg ( - ) to the radiator support so the lights are brighter. And for sure, one to the alternator. Puts the whole system on an even reliable ground. Amazing how much better things run
smile.gif


The big battery neg cable was almost always just crimped and it has developed "crevice corrosion" in the years it's been on the road. And it's never been cleaned and lubed on the connection to the block ... So even if you clean the bolt and the cable eye, it will still be slightly off. The new added grounds will help. The big cable can take the starter load, but the new cables will take the running loads and keep everything nice and equal
smile.gif

Yes all the basics need to be done. I had intermittent no starts on the tractor last week and did a load test on the battery and further testing found the problem to be corroded battery cables where the fit into the terminal connectors. That actually is a common problem.
 
Thanks to the expert advice given I've spent some time with the Zuk this morning.

New heavy grounds from - battery to the alternator and firewall, to the rad support and engine to firewall soon.

Did the tests suggested by eljefino and found 0 from - battery to alt case and 2.2 from + battery to b+ post on alternator, which shows the difference between alt output and battery charge?

The battery holds a charge overnight within a few hundredths on my meter, is it maybe OK or not? 1 cup of distilled water brought all 6 cells close to the top.

So do I replace the voltage regulator and brushes (might as well) for $70 or drop in a reman alternator for about the same money? The Zuk sees about 3K miles a year so I'm not thinking a new Denso for $140 is necessary.

Big thanks for the help. I've owned the Zuk since '02, by far the longest of any other vehicle. Resisted the urge to go big with it since that just leads to chasing the next weak part. Every once in a while we talk about selling it but just can't.
 
Heh heh BIL used to have a Tracker with Sammy for partz. When it got too rusty, he sold to a Mini Mote enthusiast (nut) I may have mangled the name. They were a Brit runabout 4wd mini. If the alt is factory, If you could find a Youtube showing how to R+R stuff on that alt, that would be good. Regardless, I would buy the regulator and brush kit maybe some bearings too. Alternators are hand assembled. To an extent, they are idiot proofed by design. Long before I realized this, I made scratch marks across things before I took them apart. I still do, cause I frequently push the bounds of idiocy in my attempts to fix things.
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A voltage regulator, brushes and bearings would be the same money as a rebuilt with lifetime warranty. It's not the OEM alternator. I love fixing things but sometimes it doesn't make good sense.

UPDATE: I bought a reman alternator from O'Reilly and put it in and am seeing the same high voltage across the b+ post and ground or - battery terminal. I guess I'm missing something here.
 
Check your voltmeter on a known-good car.

The 2.2 volts drop on the live wire is a lot. With battery charged and most electrical stuff turned off, it should be a lot less than that. Maybe it is because the alternator is overcharging and the battery itself is drawing a lot of current though.

Also check the reference input to the alternator. The regulator senses the battery voltage through one of the small wires. If that voltage is lower than what is actually at the battery, it will overcharge.
 
BrocLuno-

With all these grounds going everywhere; can ground loops can be formed which will drive the computer crazy? I think one ground with all the individual grounds connecting to it would be best?
 
How would I check the reference voltage? There are 2 wires in the plug going into the voltage regulator and they aren't accessible. Could I pull the plug while running and check them quickly?

Willbur, I'm pretty sure there's no computer.
 
Originally Posted By: AZjeff
How would I check the reference voltage? There are 2 wires in the plug going into the voltage regulator and they aren't accessible. Could I pull the plug while running and check them quickly?

Willbur, I'm pretty sure there's no computer.


True- but I was speaking in general terms regarding grounds. Your car does not have a computer, but others do and I am interested in effects (if any) of ground loops on the computer, for cars that do.
 
UP-UPDATE: This evening I turned the key to run and checked voltage of the 2 wires that plug into the voltage regulator. Both measure 9.9 volts. The battery measures 12.8 volts. I started it and the voltages all stayed the same and the alternator isn't charging with the plug out. With the plug in at idle the alternator voltage is 15.5 so the low volt inputs seem to be the issue. I guess 1 wire is the signal circuit and the other is used to regulate the amount of volts produced. Since they're both ignition switched could I find a switched positive wire and make a jumper to the terminals on the alternator?
 
Yes the two wires are likely ignition switched +12, used to sense battery voltage, and the "battery" light (alternator grounds it to turn light on).

The wiring in those cars is especially terrible. Check the fuse boxes, etc to see where you're losing voltage. Or punt and hook up a relay (and fuse) direct to the battery. Many people do that with the interior fan to make the A/C work better.
 
Good Find on the 9.9 Volts. That's likely a significant cause. The regulator thinks the car is at 9.9 V instead of ~13, so it's over-compensating at 16+ to try to bring it up.

Check all fuses for clean contacts. Check relays for clean contacts. consider swapping relays that drive IGN or ENG. Look for any wiring harness connectors that can be separated, cleaned, greased, and reconnected.

-m
 
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