`96 Firebird Engine Codes - does bad alt show up?

[Kevin - Blown 95 TA]

If he has a multimeter, he can test it the way I described (assuming it runs) and that will give him a very good indication if it is good or not unless he has a heat-related problem, or intermittant which only shows up at higher outputs after sustained use. Usually, what goes wrong in the alternators is a $.50 button diode fails short (to ground) in the rectifier circuit. Sometimes the internal regulators go bad and cause high voltage to overcharge the battery, or also no output. Also, as Kevin says, the bearings go out, so a lot of alternators & water pumps are returned for that reason as well; it was very common in the days before self adjusting tensioners - people would overtighten their belts and wreck them that way. Be wary of cheap rebuilds, because a lot of them are just cleaned, blasted, and reassembled with only the broken part repaired - they are not always totally refurbished. If you ever noticed, NAPA has 3 levels of parts you can buy in order to supply quality parts to those who want quality, and cheap parts to compete witht he Autozones and other discount parts stores. I would make sure all of the electronics and the bearings have been replaced and there is a good warranty. The only thing wrong with going to Autozone to get it tested is that they do, after all, make their living selling auto parts - but usually they are honest about it. A company called Transpo makes the majority of the parts for rebuilding alternators, so you can always see who carries their line locally and do it yourself if you are so inclined.

[Kevin - Blown 95 TA]

OK I might try a better explanation of why I said to test it this way.

A healthy battery has a nominal 12.6V. Just off a charger, or after running the car for a while, it might have a residual charge of 13V or so which will gradually go down a bit. Sometimes a low, but healthy battery might go up a bit (recover).After time, a bad battery won't hold a charge. A battery with a bad cell or a dead battery might show 10V. IF you load test a good battery, you are looking for the reserve that it has and you don't want to see much of a sag in voltage (ie: with just lights on) unless the load is very heavy like during cranking, in which case it might sag to 10V or so. You can run a car off battery alone, but the voltage will go down as you drive it, especially with an EFI car. Some guys do this at the track to not have the drag of the alternator during a run. But they have to make sure there is a good charge before blasting down the track because the voltage affects the injectors, etc.

EFI cars use a lot of current. They all have big alternators because they have elec fuel pump, injectors, six or seven computers, power this & that, big stereos, and powerful lights. When you measure your battery before the car starts and you see maybe 12.8 or 13 Volts, you will start the car, and if the alternator is working, that voltage will jump up to 13.8 or more at the battery terminal, assuming the battery is not very dead, or there is not a ground or battery terminal problem. Now, if you turn on some lights, blower, & other appliances, then you are really putting a load on the alternator. Run it at a fast idle so it can make some power. You look at the voltage across the battery - Is it still at the same 13.8V? It should be unless you are drawing 140 Amps or whatever it is rated at. The regulator will regulate voltage as long as the alternator can put out enough current to keep it up there. The sense wire (small wire at the back) senses voltage in the electrical system, and if it starts to sag, the alternator will put out enough to get the voltage back up, if it can. At this point of higher running voltage 13.8 or whatever, you are charging the battery - current is going into it from the alternator. If the voltage is 12.8 you are barely charging the battery and the alternator is barely keeping up. If it is or 12.6 or less, then you are DISCHARGING the battery and using battery current to supply the circuits in the car. The ONLY time current should be coming out of the battery is when you are starting the car or at a real low idle/heavy load for some reason (giant stereo amp). The rest of the time, the alternator is supplying the juice and charging the battery. Remember, current will always flow from a source of higher potential to a source of lower potential in any given current loop. Therefore, any time the car is running with a voltage higher than the battery's static voltage, you are loading the alternator by running whatever devices are on as well as charging the battery..

Now, as far as disconnecting a battery while a car is running, the voltage regulator cannot always react immediately to the absense of the battery's internal resistance in the circuit. This can cause a very short duration, very high voltage spike to occur in the electrical system, and can take out transistors and other semiconductors in the various controllers (there is some protection against his, but it is not guaranteed 100% effective since the spikes can be a few hundred volts or more).

[Trash man]

and boy cant u wait till we go to 42volt chargin system and 36 volt batteries lol.

im currently in training to become a tech(a mechanic replaces parts, a tech finds and fixes the problem) u can use a DVOM at the battery, if u want to can disconnect the cables to just get the battery, it doesnt really matter. to test the charge set it to volts, and hold it bout 1500 and look for something between 13.xx and 15.xx i forget the lst two digits in each.

[Kevin - Blown 95 TA]

and boy cant u wait till we go to 42volt chargin system and 36 volt batteries lol.

Yeah, i'm already working on those - also 48/56V, but for tractors & utility vehicles.

[TGregg]

Arguing is not going to help TGregg.

TGregg, you said the car died with a fully charged battery. Did you disconnect the ground to make it die? How old is the battery? Just because the battery shows a good voltage doesn't give a clear picture of whether or not the battery is good or more importantly if the alternator is functioning properly.

It is not uncommon for the drive end bearings in these Delco alternators to whine almost like a supercharger. I don't believe there is any direct correlation between the bearing whine and bad brushes or or a bad stator.

The alternator needs to be load tested. Autozone and most other parts store chains will load test your alternator and battery for free.

Hey Kevin,

They load tested my battery and it was fine. The battery was fully connected when the car died yesterday, and seemed to be fully charged since the charger said it was charged after a minute or so.

I don't think it's the alt, I think the `puter is dying on me. Or I have some intermittent connection someplace.

[TGregg]

I do have an analog multimeter. It only goes to 20 amps tho, I vaugely remember something about using a resistor to bypass most of the current (so you can test higher currents than the meter is rated for), but not sure how to do it. I have no idea what the resistance of my meter would be either.

And the car started and ran better today. Still shuddered a tiny bit tho. I swear it is heat related, when it's hot out is when it seems to have the most problems.

[Kevin - Blown 95 TA]

Is it a possibility your coil or spark module is heating up and causing missing & stall? It's a little hard to tell just what the order of symptoms are from rereading all the posts.

[Red20170]

Have you had work done on your car lately?
Have you determined where the noise is coming from?
Is the connector under the alternator pluged in? If not your car will act like it dying a slow death.
I say change the alternator if it fixes it good. If not take it back. At least we can start ruling out components and begin to narrow down the problem. Chasing down electrical gremlins for someone of the internet is very hard.

[TGregg]

Is it a possibility your coil or spark module is heating up and causing missing & stall? It's a little hard to tell just what the order of symptoms are from rereading all the posts.

Other symptoms are it plain won't start (won't turn over). Unless I have multiple problems, which would make diagnoses mighty tough. One double problem scenario would be a bad alt and . . .uhm. . . those things. What's a coil? I mean, I know basically what the electrical component is, but I don't know what it does.

[TGregg]

Have you had work done on your car lately?
Have you determined where the noise is coming from?

No, it seems to be from the engine itself. I can record it for you guys if we can upload .wavs here.

Is the connector under the alternator pluged in? If not your car will act like it dying a slow death.

Yes it is wired to the voltage regulator.

I say change the alternator if it fixes it good. If not take it back. At least we can start ruling out components and begin to narrow down the problem. Chasing down electrical gremlins for someone of the internet is very hard.

I don't think it's the alt (but you guys know more about this stuff than I). The car died with a charged and connected battery that tests fine. I'm going to try to drive it to a pro on a cool morning with my wife in another car.

[Trash man]

when does it die? over a bump or it doesnt matter? what are u doing when it dies. the more specific u can get the better the answers can come.


thats what i hate with customers, they give u bones an no meat[/rant end\]

[TGregg]

when does it die? over a bump or it doesnt matter? what are u doing when it dies. the more specific u can get the better the answers can come.


thats what i hate with customers, they give u bones an no meat[/rant end\]

Sitting there idling while I tried to run to the front of the car to figure out where the fan-like/empty pump like whine was coming from. Engine died within a couple minutes. Battery is charged and connected. Alt is wired to the voltage reg.

The other time I had charged the battery, cleaned the postive contact red thing very well (cut the plastic off, de-acidized, cleaned, filed and sanded the contacts, put it all back together) drove it to the dentist, then to the gas station where she needed a jump. Battery was in need of a charge when I got home.

I was having intermittent problems before, some of which I suspect were caused by the surprising amount of battery acid that was in the positive connector. Perhaps I spiked my computer since the battery may not have acted as a capacitor at various times for several minutes at a stretch.

I had about 8 ounces of water/baking soda, and after I had already blown off some acid, I dunked the connector sans the red plastic protector. The solution looked like milk from St. Patrick's when I was done. There was a lot.

[TGregg]

Thanks for the long explanation, Kevin. That's pretty interesting. I had no idea my car could burn 140 amps. Youzah.

[Kevin - Blown 95 TA]

You may have nothing wrong other than really crummy battery cables and a bad ground. I would replace them because it sounds like it needs it anyway, and they should be pretty cheap. That might fix a lot of problems. If your car runs sometimes, chances are the PCM (computer) is OK. If you have to, run an extra wire from the battery ground to a bolt on the body of the alternator (like one of the bolts that holds it on) and see if that helps. If it helps, you may just needs to fix the engine ground. The grounds (negative battery terminal which goes to the metal parts of the car & engine) is immensly important. Without it, current can't flow.