[cc82z-28]

I am at my witts end with charging system in my car, it is an 82 Z-28 with a 406 and my problem is that as under hood temps build up as they do in these cars, the alternator begins to quit charging. The problem was there when I had the 10si style alternator and I thought that the alternator was going bad, but turns out that as it got hot it would do the same thing when at or near idle. So I bought a Powermaster CS 130 style alternator with 145 amps, same problem, charging drops off to only 12.5 or so volts from the 14.8 before things get hot. I am still running the original charge wire that appears to be about 10-12 gauge wire but I also run a 4 gauge wire direct to the battery that is fused to help keep battery charged as well as grounds galore from the alternator case, engine and to the frame rails and body with a total of about 5 or 6 of all sizes and gauges. I run dual electric fans with a Flexalite controller that is wired direct to that battery per their instructions and when the fans are running with my headlights on at idle which is about 900 rpm, the voltage starts dropping as things get hot under the hood. The car is not overheating, just the underhood temps heat up. Before that happens, the voltage starts out at 14.8 checked at the battery and the altenator. How much heat will cause alternators to slowly stop charging or is it the original charge lead in stock wire harness? Should I wrap the headers to help keep excess heat out since the car is just my toy and does not see rain? Open to suggestions or ideas on how to combat this problem. Sorry for the long post, just wanted to be as detailed as I could. Thanks for help.

[blwn31]

Check your battery ground and the ground on the engine to chassis. Make sure the power wire to the alternator is not corroded somewhere. As the temp increases so does the resistance in wire. A volt meter won't tell you this, unless the resistance is off the chart high. This may be part of your problem. Do you have problems with 12.5 volts? If the battery is staying charged and you are not having no problems, I wouldn't worry to much about it.


Keith

[cobalt327]

Originally Posted by cc82z-28

I am at my witts end with charging system in my car, it is an 82 Z-28 with a 406 and my problem is that as under hood temps build up as they do in these cars, the alternator begins to quit charging. The problem was there when I had the 10si style alternator and I thought that the alternator was going bad, but turns out that as it got hot it would do the same thing when at or near idle. So I bought a Powermaster CS 130 style alternator with 145 amps, same problem, charging drops off to only 12.5 or so volts from the 14.8 before things get hot. I am still running the original charge wire that appears to be about 10-12 gauge wire but I also run a 4 gauge wire direct to the battery that is fused to help keep battery charged as well as grounds galore from the alternator case, engine and to the frame rails and body with a total of about 5 or 6 of all sizes and gauges. I run dual electric fans with a Flexalite controller that is wired direct to that battery per their instructions and when the fans are running with my headlights on at idle which is about 900 rpm, the voltage starts dropping as things get hot under the hood. The car is not overheating, just the underhood temps heat up. Before that happens, the voltage starts out at 14.8 checked at the battery and the altenator. How much heat will cause alternators to slowly stop charging or is it the original charge lead in stock wire harness? Should I wrap the headers to help keep excess heat out since the car is just my toy and does not see rain? Open to suggestions or ideas on how to combat this problem. Sorry for the long post, just wanted to be as detailed as I could. Thanks for help.

There is a pretty good chance the battery is letting you down. Have it load tested to see that it's capable of keeping up w/the demand.

[EOD Guy]

When the underchharging is going on, are the fans running?

[cc82z-28]

Thanks for the replies, I have checked the all the positive and negative cables for possible corrosion, find none, all are good and clean with good terminal to body or engine connection. As for the resistance, haven't checked that, not to sound dumb, but what will I need to do to check resistance? I have a digital volt meter, not all that good at it but am trying to learn, where do I start and which wires do I need to check? As for the fans running, yes the fans are sometimes running however, before things heat up, the fans running have no effect on the charging, even with the headlights and fans running, the charging will stay up to 14.0 volts. Like I said before, both alternators show the exact same problem so I am satisfied that it is not an alternator issue. As for the battery, it is an Optima battery that has not shown any issues with holding a charge, but I have not had it load tested since even when things get heated up the car starts fine. When this issue arises, my ignition starts to break up a little and my tach and shift light flash radomly until I get things cooled of by moving again. Just seems that I am not getting enough air moving around the engine compartment to exhaust the heat out. I have done all sorts of things over the past couple of years with little or no change. I have changed the temp setting on the fans to come on sooner in hopes of seeing if that can help it some by pulling air in sooner so it passes through the alternator since it sits close to one of the fans, I will see how that works hopefully tomorrow. Again, thanks for the replies and the input.

[EOD Guy]

What is the condition of the alt belt...... is it slipping when things get hot? That would cause the under charging.

[66GMC]

Originally Posted by cobalt327

There is a pretty good chance the battery is letting you down. Have it load tested to see that it's capable of keeping up w/the demand.

Ditto on this.

When it comes to conventional lead-acid batteries, summer heat kills as many batteries as winter cold.

I'm not sure if the same applies to AGM batteries or not.

This is a simple, low-cost test ... even free at some parts stores, I've been told.

[T-bucket23]

My guess is you have a bad connection somewhere. I don't agree with the battery theory as it should not effect the charging voltage. I would go over the grounds from the battery to the block and from the alternator bracket to the block. If you have a marginally sized wire somewhere the heat could be pushing it past where it can still pass enough current.

[cc82z-28]

Originally Posted by EOD Guy

What is the condition of the alt belt...... is it slipping when things get hot? That would cause the under charging.

Everything is new, belts, alternator, ground wires, straps, positive cables, and can find no real reason at this point. Thanks for the replies, and I will keep looking since, sometimes you can't see the obvious when you are looking for something more complicated. I have been bitten in the past overlooking the simple things.

[EOD Guy]

Try testing the voltage on the Neg and Pos posts of the battery..... you already know this but just for reference

Test the voltage on the large lug on the rear of the alt and the neg post on the battery..... if it remains constant 14+ volts you probably have a bad charge wire...... might try running a new charge wire to the pos post on the battery

[Houston54]

You say you checked the cables but did you check the entire length?
The reason I ask is I had a similar issue on my 54. As the operating temps rose the Volt meter reading would go from 14V down to 12V or less.

Thinking the alternator was bad or I had a huge drain due to my AC system I increased the Alternator to 140A and still had the problem.

A thorough tracing of the cables found where the positive cable going to the starter had rubbed through the insulation. Once that was resolved I have had no further issues. Worth a look.

[T-bucket23]

The key here is to check what is missing when it stops charging. You are eiher loosing a ground somewhere, loosing the feed to excite the alternator or the battery connections are failing when hot. When it stops working it should only take a couple minutes with a volt/ohm meter to determine the cause.
The alternator basically needs a ground, a hot feed to the large stud and voltage at the exciter wire. You are loosing one of these items.

[cc82z-28]

Thanks for the replies, I haven't been online for a while due to famly medical issues. I took the battery out today and had it load tested and it came at 670ca out of 710ca available. So suffice to say it isn't the battery, I run the ford solenoid setup on my camaro and have done so for the better part of 15 years. The cables look ok but you are right, it could be something within insulation that I cannot see such as corrosion which happened to me on my truck many years ago, didn't see until I pulled the cable off and split it open to find alot of corrosion. I am running a new powermaster 140 amp cs130 alt with one of the exciter wire jumpers from Napa that hooks to the factory harness. Just like what was said above, I am losing voltage as the underhood temps rise even though the car is running only 180*-190* temps. As it heats up, voltage will drop to the point of the ignition starts misfiring and my tach jumps erratcially, and the shift light starts randomly flashing. As I increase rpms, voltage will come up some but not to the 14.5 volts that are there when there isn't the heat yet under the hood. The maddening thing is that up until last summer and now this summer, I have not any problems with the charging system and all the accessories and fans have been on the car for the better part 3-4 years so it's not like I have added something new to the car. The stereo is stock GM, no amplifier and I have no other electrical gadgets, no power windows, door locks, hatch pull down. I will do some more checking over the next couple of days when it is acting up and get some more info to post and post a pic of my setup. I run no less than 3 heavy negative cables as well as 3 braided cables from the engine to the chassis. Again thanks for all the replies, I will let you know if I find anything else as well as when I finally find and fix the problem. I have a never give up attitude.

[cc82z-28]

Well, I thought I would give an update to my problem, turns out that the connection lug at the end of the positive battery cable had gotten loose over time. When I put the remote solenoid in to solve a hot start issue with the camaro years ago, I had taken the positive cable off and shortened it and then with provided connector I had to crimp on to get the length I needed which is only about 12" long. I pulled the cable off the battery and did ohms test and found high resistance when moving it around, so I recrimped the connector and the ohms meter indicated it was now good, there was no corrosion. I reinstalled and after driving the car seveal times with the fans running and the headlights on, the charging worked as it should. Glad I went with the cs 130 style alt since it has the output needed at idle to work. Thanks for all the replies and the help, much appreciated.

[EOD Guy]

Good to hear you got it fixed