A little "off topic" question for you great electrical guys ???

-
'70_Duster_340

'70_Duster_340

Well-Known Member
Joined
Aug 15, 2007
Messages
459
Reaction score
0
Location
Connecticut
I know this is an A body forum, but hopefully one of you guys can shed some light on this for me, and you've never steered me wrong yet..

We run class 8 trucks, with Detroit engines and have been having a NIGHTMARE with alternators the past couple months ...

After 3 years, one of the stock Delco alternators crapped out .. We installed a new after-market one and it was fine for a few weeks, and then it started WAY over-charging - up to 16 volts ...

Since then we have tried 3 different re-man Delco's and they are all fine for a while, charging between 13.8 and 14.2, but two had to be changed because they suddenly started dropping to 12 volts, and another was spiking at 16 volts..

We checked all the connections, re-did the chassis ground, and the batteries are less than a year old and check out fine w/ a load tester ...

We're guessing they are just crap internal voltage regulators, but don't really know ...

Anyone have any ideas ???

Thanks as always,

Kenny
 
68_val_sedan said:
Where are you getting the reman alternators from ?
Click to expand...

3 of them came from a local shop that we've dealt w/ for years .. We found them and we're impressed because they always prided themselves on using "better than stock" replacement parts ... I'm not convinced that is the case these days..

The 1 we installed today is a "factory" re-man, straight from Mexico, so we're hoping THIS one survives ..
 
I ran into this with a friends car years back. In that case it ended up being "sloppy" voltage regulator adjustment screws. Would work good for a while and then with the rumble of the BB and open headers it would gradually turn itself. Its really not an issue with stock or near stock engines. Maybe ask your local guy if they hit the adjustment screw with loctite when they rebuild the alternators. May not be what your problem is but I thought Id mention it. Good luck!!!
 
Thanks, that's a thought .. The regulator is built into the alternator and I'm not sure how that all works.. It's just weird that sometimes they fail due to high voltage and sometimes low.. Is that regulator adjustable ? That would make sense as there's a lot of vibration and pounding under the hoods of these Sterlings..

Thanks

Kenny
 
Yes it is adjustable, its set when the alt is tested during rebuild. Another thought, maybe check the specs on the wire gauge requirements coming into and out of the alternator. If even 1 wire isnt the correct gauge it could cause an alternator to fail. Good luck and let us know how it ends up.
 
When GM first startered using those electronic regulators They added diodes in a crowd of places to protect the regulator from voltage spikes at switch off. Most obviuos was the one on the harness plug to a/c clutch. I've oftem wondered how they hold up when aftermarket electricals like cooling fans, etc.., are added to the system. It helps to have the battery ground directly the altenater or as close as possible (current takes the path of least resistance).
If you'll buy a quality regulater ( NAPA I guess ) and take one of the failed altenaters to the workbench you will find its a pretty simple task (30 minutes) to R&R the regulator rather than replace the entire unit.

I dont recall seeing an adjustment screw on a solid state regulator.
Good luck
 
I ran into the same on my 454 Suburban, went through 3 and a battery before I got a good one. And 2 years ago on my diesel F250, I went through 4before I got a good one. Bought from Advance Auto and Napa. Some undercharged and some overcharged. Everybody just acted like they were crap parts and gave me a replacement. I did have to raise a fuss at the Advance Auto when theirs cooked my battery. They didn't want to replace the battery. A friend of mine recently put a regulator on his Harley. He got it from Auto Zone and it overcharged and cooked his battery. He sued them for a new battery. Good luck...it sucks to put a new part on and break down the next day because of the new part.
 
Thanks for all the insight guys, it's truly appreciated .. I'm gonna print this thread out and save it ...

True, there is nothing more frustrating than putting in a new (or re-man) and have it fail 4 times ..

Red, the main battery ground that ties all three batteries together is inside the frame of the truck .. We took that off, sandblasted everything bare, re-installed and painted over everything to keep it from rusting..

The ground on the alternator runs under the engine to the starter, and then to the batteries.. Do you think I should add an additional ground directly to the batteries ??

So far today, the latest re-man has worked perfectly, but I've been "here" before-only to have it fail in a couple weeks... We'll keep a close eye on it..

Thanks again guys,

Kenny
 
The problem is the junk electronic regulators were getting overseas nowadays. Quality has gone the way of big bucks. Good luck with the Mexican junk but I think you'll find it's about the same as the rest. I worked on Hyster forklifts for over 10 yrs. and they used gm 4 and 6 cyl. engines with Delco alternators. I was forever changing them. I sware I did so many I could do it blindfolded. Allways buy new parts if you can. They are usually made to a higher standard from what I've seen. You'd be surprised at how little the difference in price there is too. You might run into trouble with parts counter monkeys not knowing how to get new parts. If he says they don't have it ask the manager. I know napa and O'Reilleys can get most of these parts new. It's just a matter of finding the right parts guy that will actually get off his butt at the computer and look in a book to find it.
 
I have rebuilt a number of the old 10si and 12si delco alternators and one common issue is the diodes. get yourself a set of heavy duty diodes from a local electrical rebuilder made for something like a 120 amp unit and that will cure the common voltage drop problem. as far as the spiked ones they usually end up being something inside the alt. not making a good connection so the regulator thinks its an open circuit and starts overcharging. i have had good luck with the replacement regulators from borg-warner, they seem to make a quality part.
 
You must log in or register to reply here.
-

Back
Top