Thread: 10SI voltage regulator fails repeatedly

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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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Mike P, if nothing else it's great to hear I'm not the only one dealing with crappy voltage regulators. Have you experienced the failure intermittency I'm dealing with? I will take your suggestion and buy a spare and in the interim start keeping my lights on when driving. Regretfully that's about the only load I can put on the alternator. I do know that when the regulator starts to fail (ammeter starts climbing) turning on the headlights doesn't help.

Originally Posted by DennyW

Read through this, and see if it helps on your problem.
https://talk.newagtalk.com/forums/th...layType=nested

Thanks Good Read