I had an intermitant voltage issue going on with my fresh delco reman alternator. sometimes it would charge, sometimes not. So, since the alt only had ~3k miles on it, I checked grounds, ran jumper wire from PCM to plug on alt (eliminated potential of broken exciter wire). Turned out to be a bad stator. Took it to an alternator repair shop and then replaced with a heavy duty stator and retested. Put out 125 Amps. Put it back in my car and it works fine at idle and normal driving.

HOWEVER, at WOT and night, i can see the headlights dim and the watch the voltage gage go down. As soon as I get out of the gas, it goes right back up to above 13v on the gage. I just took it out last night after putting it together and have not had a chance to hook up my volt meter. I could data log as well and look to see what RPM the voltage starts to fall off at.

Did some searching and found a lot of fluctuating voltage at idle issues and what not.... All connections are good, wire from PCM is good. Alt shop said it tested out perfect but will install a HD voltage regulator if I want. Saw posts on the truck alternator as well, but since mine was putting out 125 amps I figured it would be fine. Unless the regulator is the culpret????

Contemplating putting a procharger on this car and definitely want to get this crap ironed out prior to that!

Thanks
Brad

 

How's the condition of your belt tensioner/idler pulleys etc.? Possible belt slip?

If not that I'd consider a regulator issue...

 

all that stuff is good. No issues with the power steering or any belt noise either. PS would be even more likely to show issues of belt slip I would think since I am ripping corners with 315's front and rear.

I am going to put it up on my lift to pull it out, and will look for any belt dust by the alt. Should be nothing since I only drove it 5 miles......

Since I have a 6.0L and it does not have a tab where you can install the center bracket bolt, I am not to thrilled about trying a truck alternator if I can't use the rear mounting location. I did drill and tap one of the holes, but the center one physically does not have a boss behind the bracket on the block. Right now I have 3 mounting locations, top, bottom and rear.

 

even with a 6.0 block and losing a bolt......i think its plenty strong to install a truck alt....the rear bracket is useless IMO

 

I wonder if there is some load shedding strategy like with the A/C,
that drops out field current to free up power at WOT. Kind of a
long shot conjecture, I haven't observed it on mine. But then I
am not usually looking at gauges when WOT, and my battery is
stout.

My '79 Sportster developed a brush-skip problem where it would
charge fine at low RPM but cut out at highway RPM. Seems like
another long shot but with a reman alt there could be a brush
or ring issue that got missed or not-inspected-for.

You might put a meter on the exciter wire and eyeball it at WOT
to see if it's really staying right, or moves abruptly just when it
cuts out.

 

Good idea. Easy to check, I will just take up in rpm at half throttle and see if it does the same thing.

 

car still does the same thing!!!

When cold alt works just fine.

When hot after driving for a while, it will do it at BOTH WOT and just rolling into it.

I put it in 2nd and gradually reved it up to 6000 rpm.....
right around 4500 rpm, the lights went dim and voltage dropped on the gage.

I took the alt back and everything has been replaced. They tested it to 10k on their bench and got it good and hot and can't reproduce the problem.

This leads me back to a PCM issue??? I have tried bypassing the wire, but am wondering what the PCM may be commanding it to do??? Any thoughts?
thanks
Brad

 

have your charging system checked. if the battery is putting out more cranking amps than its rated for then that could be a voltage regulator issue in the alt. also do the big 3 and completely clean the grounding spots. im having some voltage issues to and im down to doing the big 3 as my last troubleshooting steps.

 

what issues are you having? My car only has 20k on it and has only seen rain a couple times. Everything looks good. the race tronics set up includes an extra ground to run from the batt to the fender well. Just inspected the ground strap from the body to the block and it all looked good. I suppose i could run an additional one, but don't see how that would be necessary based on the size of the other one.

Even belt slip shouldn't do this since it puts out 13.6 at 850 rpm. It would have to stop to not put out when the motor is above 4500 rpm and I would definitely hear that belt queal!

 

ever get this worked out? My car does the same exact thing. I am on my 2nd reman AC Delco alternator. I am swapping it out tonight for a brand new Remy. I hope hope hope this will fix the problem. My first AC Delco the voltage would drop past the middle line on the gauge at WOT and the lights would dim. This current one I got to replace the failing alternator...wow...the voltage will drop so bad that the check gauges light will come on. It also does it on decel if im engine braking...what. the. ****. lol

 

get a truck alt.............or bigger

 

https://ls1tech.com/forums/generatio...-failures.html

 

I had the same problem, WOT the voltage would drop right down to almost nothing. It happened with an autozone alternator, then I got a REMY, worked good for awhile, then started doing it again. I got a new REMY under warranty and have had that once for about 15,000 miles now, no problems.

I bet its the alternator, mine tested out fine at autozone but it was the problem.