Thread: 10SI voltage regulator fails repeatedly

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I install a new (NAPA rebuilt) alternator and all is well for anywhere from a few minutes to a few months. This last time it was just a few minutes. Start the engine after the install and all is well. Hit the road and after a few minutes I can watch in frustration as the ammeter begins it slow climb until it's pegged. It took maybe 3-5 minutes to peg. On other occasions this would happen and then repair itself but in the long run it got to the point that the ammeter was continually pegged. It's in an L98 in a 58 Vette that doesn't have A/C or much of anything other than electric fans. I don't see any evidence of the battery boiling and there are no codes being thrown. Output voltage at these times is 15-15,2 volts. IDEAS PLEASE!!!

I think as long as your driving it I would just put in a one wire Alt. and eliminate the V.R.

Originally Posted by cffisher

I think as long as your driving it I would just put in a one wire Alt. and eliminate the V.R.

That sounds an awful lot like I'd be ignoring the real problem - whatever the hell that is. I know lots of folks use these 10SIs without this issue.

This "new" 10SI alternator is an internally regulated alternator? If so, did you take the external regulator out of the car? Just asking...
Mark

How high does your ammeter read? 15 to 15.2 volts does not sound terribly high to me. Are you sure there is actually a problem? If there is a problem, it could be a defective battery drawing excessive amperage.

He's saying his ammeter is showing high reading.

Then he specified a volts reading.

That is quite conflicting.

Volts ain't amps.

Mr Natural needs to refine his original post, with more information if possible.

My knee jerk reaction is:

He actually has a volt meter, not an ammeter.
If so:

If you have no secondary issues, then the volt meter is the first suspect. An easy check is to plug in a volt meter to the cigarette lighter socket. You can watch it as you drive and compare.

Telling us the engine is an LS doesn't tell us much about the alternator. Biggest thing to know, internal or external regulator?

Probably internal.

If a second guage agrees with the first, and it is internally regulated, then replace it. If external, then replace the regulator.


Other things to check:

Grounds. Make sure your ground wires are in good shape, and the star washers are great for making good connections.

The plug into the alternator, it is suspect. Was it a new wire harness or a swap? Replacement plugs are available at your local parts store.

Let us know, and good luck.

Originally Posted by astroracer

This "new" 10SI alternator is an internally regulated alternator? If so, did you take the external regulator out of the car? Just asking...
Mark

Astroracer, the external regulator is long gone. I totally rewired this car with a new harness and then some custom work to accommodate the L98 350. That was more than 10 years ago.

Firebird, I've got the stock gauge which is an ammeter. The gauge pegs at 30 amps and when all is running as it should the gauge registers about 8 amp. I'm getting my voltage reading by using a VOM at the alternator. The 10SI is a GM stock 63 amp alternator with an internal regulator. I would suspect a defective ammeter if I didn't have 15+ volts at the regulator, plus ammeters are pretty much bullet proof. Grounds are good - I've checked them repeatedly. I'm not aware of any secondary issues.

Originally Posted by Driver50x

How high does your ammeter read? 15 to 15.2 volts does not sound terribly high to me. Are you sure there is actually a problem? If there is a problem, it could be a defective battery drawing excessive amperage.

Driver, please see my reply to Firebird. You do bring up another possibility in a defective battery. It's fairly new from Costco and if memory serves I had this problem with the old battery that failed one month past the 36 month Costco warranty.

JMHO, but it appears to me you have two issues;
1) Excessive current draw after the ammeter. I say after because the ammeter only register the current draw going through them, and ammeters are usually wired on the accessory side of the circuit (no starter load).
2) The regulator is not operating/sensing correctly causing a high output voltage (15+ volts is too much).

Believe it or not, both conditions can be caused by poor/bad connections, including but not limited to grounds. A poor connection causes resistance, in turn lowering the voltage to the appliance (what it is connected to), causing current to rise. A bad MAIN ground connection can cause the regulator to increase voltage as it's sensing through the resistance and adjusting (additionally the ammeter would read high).

Try grounding your alternator directly to the battery (jumper cable), if the alternator's output voltage drops to an acceptable voltage (14 -14.7 volts), then you have a poor ground connection between the battery and alternator. It may be at the motor where the battery ground connects.

I personally do not like the idea of 100+ amps of electrical current seeking ground through my motor (and its moving parts).

I run separate grounds to every electrical appliance, especially when connected through the motor. Alternator, A/C, Fans, cylinder heads (yes spark is and appliance), exc.. Some will say this is over kill, and in some cases (stock) they may be right. I'm not a gambler, and I've seen what current can do, so I ground everything....

Good luck

You're probably got the ammeter shunt resistor going into meltdown. The original '58 generator was about a 30 amp so the shunt was sized for it. When you're pegging the ammeter the shunt is getting extremely hot and may be the cause of your failures. You may want to try bypassing the ammeter by tying the two wires together with a small screw and nut, tighten it good and tape it up good. Then see if your alternator problems go away.

Originally Posted by JOATMON

You're probably got the ammeter shunt resistor going into meltdown. The original '58 generator was about a 30 amp so the shunt was sized for it. When you're pegging the ammeter the shunt is getting extremely hot and may be the cause of your failures. You may want to try bypassing the ammeter by tying the two wires together with a small screw and nut, tighten it good and tape it up good. Then see if your alternator problems go away.

Joatmon, that's an interesting observation that just may be the problem. However, since the alternator is putting out >15 volts when the ammeter is pegged I'm not too inclined to believe that the resistor is the issue. And here's an update: Wife and I went for a cruse Saturday to Cave Creek which is about a 30 mile round trip and the ammeter was rock solid at 6 amps after it settled down after starting. Just like the last alternator the problem is intermittent. And speaking of intermittent take a look at another post that I'm going to post in a few minutes.

Originally Posted by 36 sedan

JMHO, but it appears to me you have two issues;
1) Excessive current draw after the ammeter. I say after because the ammeter only register the current draw going through them, and ammeters are usually wired on the accessory side of the circuit (no starter load).
2) The regulator is not operating/sensing correctly causing a high output voltage (15+ volts is too much).

Believe it or not, both conditions can be caused by poor/bad connections, including but not limited to grounds. A poor connection causes resistance, in turn lowering the voltage to the appliance (what it is connected to), causing current to rise. A bad MAIN ground connection can cause the regulator to increase voltage as it's sensing through the resistance and adjusting (additionally the ammeter would read high).

Try grounding your alternator directly to the battery (jumper cable), if the alternator's output voltage drops to an acceptable voltage (14 -14.7 volts), then you have a poor ground connection between the battery and alternator. It may be at the motor where the battery ground connects.

I personally do not like the idea of 100+ amps of electrical current seeking ground through my motor (and its moving parts).

I run separate grounds to every electrical appliance, especially when connected through the motor. Alternator, A/C, Fans, cylinder heads (yes spark is and appliance), exc.. Some will say this is over kill, and in some cases (stock) they may be right. I'm not a gambler, and I've seen what current can do, so I ground everything....

Good luck

JHMO I've checked and rechecked grounds but I get your point - maybe I missed something. Next time the alternator starts misbehaving I'll do as you suggest and ground the alternator directly to the battery.

I know that problem

I've been working on this post for the last couple of days in between other things I needed to take care of so sorry for the late reply. Long posts can be a pain to read so I'll do a quick synopsis in this post and follow it with the detailed one so you can draw your own conclusions if you want to wade thru the longer one.

As quick as the regulator went out this time I think would probably be a bit suspicious of the battery.

and

As 36 sedan indicated "........The regulator is not operating/sensing correctly causing a high output voltage (15+ volts is too much)........" is also a prime suspect.

I think you may find the real problem you are fighting are crappy regulators and good luck finding a quality regulator either on the shelf to put in or in a rebuilt alternator.



.

I'm afraid all I can do is offer a long winded reply but no real solutions.

I run internally regulated 10SIs on 4 of my current vehicles (83 El Camino 500 Caddy powered using the stock el Camino electrical system......87 Ram 50 (283/T5) retrofitted with a 10SI to the stock electrical system, 1957 Plymouth (Hemi Powered) wired from scratch and using a 10SI, 37 Dodge Pickup (Hemi powered) wired from scratch). I also recently sold an 84 El Camino that was also factory wiring and a 10SI.

I listed the vehicles to show the disparity of applications and wiring systems.

All the vehicles with the exception of the 37 Dodge have been driven cross country from Arizona to Illinois (1500 miles one way) with some trips only stopping for gas and bathroom breaks. All the vehicles suffered from the same problem.....about 300-500 into the trip the alternator would start over charging eventually full fielding (16-18 volts). The problem always turned out to be the regulator failing. Two instances resulted in ruined batteries from over charging. I went thru changing regulators or replacing the alternators with rebuilds and the regulators would always eventually fail (some quicker than others). I double, triple and quadruple check the wiring on each vehicle and never was able to find a problem with it.

Besides using 10SIs on my own vehicles they were my go to alternator when converting customers cars from generators to alternators back when I was running my shop. In the process of trying to figure out what was happening it struck me that I had not had not run into this problem until about 15 years ago. That led to relooking when the problem would start happening.

Symptoms/Issues

1. The wiring on the cars had been checked and it keeps occurring regardless of where the alternator had come from......Napa, O'Reilly, Auto Zone, or even if I had taken the alternator apart and just replaced the regulator and put it back in service. It didn't make any difference if the battery was lead acid or Gel-Cell.

2. Under normal everyday driving conditions to include the occasional 150 mile trip to Tucson and back I with one exception I never seemed to have a problem with the alternators. That one exception was a rebuilt alternator (regulator) that failed after less than a month of everyday short trip driving.

3. On the trips back to Illinois the problem never started when I was driving at night (with the headlights on). The voltage would always start creeping up (regulator failure beginning) when the car had minimal electrical load i.e. driving with the lights off/AC off during the day and at a steady 2500-3000 engine RPM and after a few hours on the road.

4. The one alternator that did not have a problem and has lasted the last 4 years on a daily driver was one that I replaced the regulator in. I had found a NOS Delco regulator that was at least 25 years old and used it on an alternator that had eaten the regulator. Right now I'm kicking myself because as I write this I just realized that alternator was on the El Camino I just sold.

5. One thing that seems to help is keeping a load on the alternator. The last couple of trips back to Illinois I found that running with the headlights and/or AC during the day I could make the round trip without any alternator issues.

Conclusions/Solutions:

The conclusion I keep coming back to is that the quality of the currently available regulators is not as good as they were 15 years ago and chances are they are all coming from the same 1 or 2 overseas factories.

The OP comment "........ I know lots of folks use these 10SIs without this issue........" holds true. That being said at this point in time most of the vehicles currently using the 10SI alternators are either in peoples toys or vehicles that are used locally for relatively short trips. As I mentioned above my experience has been the problem normally only shows up on extended drives during periods where the alternator is only pulling a minimal load.

My fix (bandaid) is pretty much as follows:

On extended drives I try to always keep a load on the alternator, at a minimum running with the headlights on.

I always carry a spare alternator with me. In my particular case I've started using the life time warranty Auto Zone alternators.......they seem to last as long as anyone else's to include NAPAs. Almost any decent size town on my route back to Illinois has an Auto Zone and usually a replacement alternator on the shelf.

Believe me if anybody out there sees something I'm overlooking or haven't checked I'm more than willing to listen.




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