Thread: 10SI voltage regulator fails repeatedly

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I’ve had past issues with these rebuilt alternators and the low quality rebuild parts they use in them. You can buy a brand new AC Delco 10Si on Rick Auto for about $80.

Thanks for the reply.

Personally I will never again use an ammeter in a car, as one burned up on me, and destroyed the car.

Again, good luck.

In all the older cars and trucks that I rebuild that have Amp meters they are wired out. All the new appliances in cars is to much for them, and they really serve no purpose. If it is wired right a fuse will blow before the meter shows a problem

I second the ammeter removal comments! They have been proven to be dangerous, a voltage gauge will tell you all you need to know.

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

I had a similar issue with my one wire alternator in the coupe. When I originally installed and wired it up, I did as the alternator supplier directed and ran the battery wire from the alternator to the battery. Later when the car was more completed, I had moved the battery to the trunk and moved the battery wire to the solenoid (battery side) this was at the front of the car.

I then began having overcharging issues. Pulled the alternator twice and took it apart, didn't see anything apparent going on so I took it to a shop here and they put it on their tester and gave it back saying it's fine??? I re-installed it and within hours it was over charging again. So I took it back apart and asked the shop to open it up and let's see if they noticed any issue. They did find a "wonky" regulator, very cheaply made and one of the contact blades was breaking off. So we replaced that and I put it back in with zero change! GRrrrrrrr...

Later I was thinking that the problem only showed up after moving the battery to the trunk. And the only thing that was still different, was the power wire not directly attached to the battery but at the other end of the cable at the solenoid connection. So I ran a #8 wire from the alternator directly to the battery terminal and wallah... no more overcharging! I don't know why the 2 ends of that big cable send a different signal to the regulator.. but it does! Maybe 36 can explain? He's an electrical wizard and has helped me many times to keep the smoke in the wire....

Since were kicking this around my wife's 03 Trail Blazer has a volt meter in the dash it's supposed to read battery voltage. While out driving long trips or short the meter begins to peg out. First time I got concerned and checked the battery it was fine. Now it pegs it out so far it won't come back. Still OK at the battery. I'm sure its the meter as there is NO WAY I'm getting 20+ volts at the battery. I have no idea how this happens and I'm not going to check any more. JUST INFO enjoy

This is an interesting thread. I’m planning on taking my T Bucket on a long trip this summer. It has a 10SI. I had not considered carrying a spare alternator. Now I’m wondering if I should rethink that. I wonder if the new Delco alternators are better than that?

Since space is so limited in a T, you might just consider carrying a new regulator and a few tools to change it with. Since the pulley doesn't have to come off, it wouldn't be too hard to change, if needed. Don't forget a paper clip to hold the brushes back for reassembly!

That is a good read Denny, I came across it a couple of years ago when I was researching the the problem.......a lot of good info, but unfortunately nothing that helped in my case. It does list some thing that should be checked and tested.

Mike's suggestion on carrying a regulator is also an option. A couple of small items that come in handy are a multimeter and test light.



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I always like to carry along a 3-4 foot long jumper wire as well. That has saved the day on several occasions.

Originally Posted by Mike P

A couple of small items that come in handy are a multimeter and test light.
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The cheapo Harbor Freight mutimeters work well enough for side of the road diagnostics. I've gotten them free with a coupon and even if you a have to buy one, they're less than $10. They are small enough to pack easy, too.

My good Fluke MM takes up as much room as 3 or 4 of the HF units and I wouldn't feel too bad if the HF meter got stolen or trashed.