Alternator issue again, advise on upgrades?

[k5ontherocks]

I am experiencing another electrical issue with my alternator on my M931A2. First one went dead, caught fire, locked up. had it rebuilt and all was good for about 100 miles. Then CTIS went out, then few days later as driving noticed the ABS lamp on,followed by noticing that the volt gauge was pegged past the red. I have been over my grounds and such and all seem to be good. My voltmenter wouldnt work last night so i will pick up a new one on way home and test a few things. I am wondering if anyone has done the Delco 27si upgrade. I did search and found very few results. Modifing the brackets would be no issue. I am a little aprehensive about the wiring, looking for an example to follow. I really like the price difference in the delco vs OE.
Any advise or input on my issue would be great.
Thanks
Andy

 

[juanprado]

I would start by checking to make sure all 4 batteries are good. Load test them if at least 12.4ish. Charge if not and check specific gravity if wet cell battery.

Sounds like your voltage regulator on the alt went south.

Alt can fry trying to charge a dead system. Ask me how I know ....

 

[swbradley1]

At least I'm not the only one who has fried their alternator trying to charge a dead system......

 

[k5ontherocks]

My batteries are brand new hawkers. Load test perfect.
I have never had a single issue starting, suspect the rebuilt alt just wasnt rebuilt well enuff. I did have a new regulator installed with rebuild.
Alt was not hot and smoking this time,just showing overcharge. i was going to try and remove the plug off the back of the alternator and see if i could adjust the output.However, it worked great for a while,dooubt its an adjustment.
Anyone done the delco 21si swap?
i have a used alt i am gonna swap out, but given my track record, the delco swap looks like a better option..
Thanks.
Andy

 

[k5ontherocks]

So far ive figured out I have good grounds, and am getting 35.7 volts at the batteries.I feel its the alternator, I will swap out the used one tomorrow and see what happens. Regardless, I think I will be doing some type of upgrade to a more modern alternator.

 

[Suprman]

You can probably just swap the regulator on the back. You don't even have to remove the alternator to do it. They are around 70 bucks new. I kill them all the time.
Will

 

[Postman515]

Just did my second swap to a Delco 21si on one of my 929a2's. Pretty simple. You just need to grind out a notch on the existing top bracket and make a longer lower adjusting bracket. I drilled out and tapped the holes on the top bracket to accommodate the bigger bolts needed for new alternator. Made a spacer for back bolt hole on rear of new alternator. Taped off the exciter wire and just hooked up ground and positive wire. I replaced the pulley on one truck and on the other I just had the pulley turned down to the right size to fit the Delco shaft. Someone posted pics awhile back of the same conversion I did.

 

[davo727]

http://www.steelsoldiers.com/showthread.php?85317-M925A2-Delco-Style-Alternator&highlight=delco

 

[k5ontherocks]

Thank you for the info. I swapped out my regulator today with a used one I had here. It did fix the issue but the delco upgrade is still going to happen.

 

[k5ontherocks]

ok, I really need some help now. Just got done with my delco swap and I am having the same overcharging issue. idle charges at 30.5v and as I increase RPMs is climbs to 35v.Ive read the TMs,and just have no clue where to start next.

 

[Postman515]

Bad battery maybe?

 

[k5ontherocks]

Batteries all load tested goor this weekend at Orileys. Having alternator bench tested today. Anyone seen a bad PCB box do this? Thats my only other guess. Ive been over the grounds several times. They are good.

 

[Tow4]

Try a different voltmeter.

 

[FloridaAKM]

Are you using a good quality DVM or just a cheapie? The cheapies might work okay for some things, but you need concrete info to keep from damaging your batteries or worse!

 

[k5ontherocks]

I have used the $9 d.v.o.m. from Harbor Freight as well as the several hundred dollar Fluke meter from work. both read the exact same. I took the batteries to a nationwide known auto parts store to have the load tests done. They used their equipment to determione the batteries were fine. The truck has set for weeks at a time and always strted flawlessly. I had my brand new alternator bench tested this morning. Saying its bad, jumps to 35+ volts as soon as brought off idle. So i have a warranty replacement on the way> Is it possible something on the truck is burning up these alternators? Or am i just having a rash of bad luck?
Ive been over the grounds on the truck very thoroughly, they are fine. Could the PCB box cause this?
thanks

 

[Artisan]

Check the main battery cables from the battery's to the starter.
Do EVERYTHING it takes to make SURE the insulation has not
worn off someplace.

I MEAN LOOK AT EVER SQUARE INCH OF IT!

 

[cranetruck]

A bad connection will kill your regulator. Say that the alternator is going good and happily charging your batteries and suddenly the connection is broken. This interruption will create a high voltage spike and ruin parts of the regulator. Technically it's called a "load dump" and you can google it for more info.
Make sure all connections are solid.

 

[k5ontherocks]

Cables are good. I spent 2 solid days going over every inch of wiring and redoing all the grounds.
I scored a test alternator last night. That seems to be the issue. Truck was fine. Im guessing i have just had a rash of bad luck with
alternators or i have a PCB box thats intermittently acting up.
Down side of all this is that i thinnk ive fried my ABS box. I now have a steady ABS lamp on the dash and no clicking noises from it as i cycle power..****..

 

[k5ontherocks]

From what ive read. And I in know way know this to be accurate or fool proof. but the delco alternator has a "load dump" protection circuit.

 

[k5ontherocks]

OK,just an update. New alternator seems to have fixed most of my issues. I did have an ABS light come on while the issue was occouring. I have found my 15 amp fuse blown, new fuse blows as soon as power switch turned on. Im guessing alternator overcharging took out my ABS unit. Ive been over all the diag, no luck. Gonna try and test the module itself tonight to see if i can find any issues with it.