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

[TGregg]

Hold on, you're saying that the alternator only has one wire on it and that's it? There should be another connector at the bottom that plugs into the voltage regulator. If this isn't plugged in, I would think it could cause a problem. Verify that the regulator is hooked up first.

I'll go check right now.

I was wrong. There's a thin red wire that connects to the bottom of the alternator, guess that's to the voltage regulator. And a ground as well.

[Christopherrr]

Very close. But I would crank the car without anything on then disconnect the battery. Then rev it to ~1500 RPMs. Then start turning on things. Turn on the A/C, slowly turn up the fan. Then the lights then high beams then rear defroster. If the engine starts missing or dies at any time during this the alternator or regulator is bad. It's a poor mans load test.

Thanks Chris

I'll write that down.

[Z Ya Later]

I'll go check right now.

I was wrong. There's a thin red wire that connects to the bottom of the alternator, guess that's to the voltage regulator. And a ground as well.

Ok, good. Just wanted to make sure that was still present . If you do end up replacing your alternator, be wary of where you get it. Rebuilds are notorious for being hit or miss. If you've got the money, Powermaster sells a nice 140 amp unit. I've got a chrome one in my Z and love it. Just another option.

[TGregg]

Thanks, but I don't think it's the alt. My last post on the first page of this thread describes my current problem, where the car died while idling with a charged battery.

The car is obviously possessed by demons.

Unless you are suggesting that bad alt could indeed cause this behavior? Y'all know way more about cars than I do.

Using what little I know, seems like there are two possibilities, either some intermittent disconnect someplace (bad wire) or the PCM is going bad.

[Kevin - Blown 95 TA]

Maybe a bad ground connection.

Basically, a battery is 12.6 volts. 2.1v for each of 6 cells. If you throw on on a charger, it will pump some more electrons into it and it will have a temporarily greater charge of 13.xx volts. All you have to do to test an alternator is to make sure the battery is properly charged (not run down) and then run the car at high idle with the headlights on and stereo blaring and see if you got 13.8v or so at the battery. I don't think disconnecting a battery on a computer controlled car is a good idea. The battery acts as a capacitor and absorbes a lot of noise spikes that the alternator and every thing else makes.

[Jeff_in_Atl]

Maybe a bad ground connection.

Basically, a battery is 12.6 volts. 2.1v for each of 6 cells. If you throw on on a charger, it will pump some more electrons into it and it will have a temporarily greater charge of 13.xx volts. All you have to do to test an alternator is to make sure the battery is properly charged (not run down) and then run the car at high idle with the headlights on and stereo blaring and see if you got 13.8v or so at the battery. I don't think disconnecting a battery on a computer controlled car is a good idea. The battery acts as a capacitor and absorbes a lot of noise spikes that the alternator and every thing else makes.

Yes it does which is why I said not to use the radio. The radio varies the load a lot where the A/C, headlights, and defroster use a pretty constant flow of electricity.

If you do not disconnect the battery you can not load the alternator. The car doesn't care where it gets it's power from. If the alternator is bad and you have a good battery you will not get the car to fail the test. Since these cars do not have an amp meter you can tell from the dash. A volt meter tells the condition of the battery. An amp meter tells the condition of the alternator.

[TGregg]

So guys, we are in agreement, right? Since it died with a charged battery, it can't be my alt, and must be either wires (maybe grounds, includes connections) or PCM or some device putting a way heavy load on the system. The parts websites call for a 140 amp alt, man that is a crapload of electrons. How much would a 140 amp alt kick out at idle speeds?

And if I need a new computer, how hard are they to replace?

96 Firebird Formula, 5.8L/350CI

[Jeff_in_Atl]

So guys, we are in agreement, right? Since it died with a charged battery, it can't be my alt, and must be either wires (maybe grounds, includes connections) or PCM or some device putting a way heavy load on the system. The parts websites call for a 140 amp alt, man that is a crapload of electrons. How much would a 140 amp alt kick out at idle speeds?

And if I need a new computer, how hard are they to replace?

96 Firebird Formula, 5.8L/350CI

I didn't say that.

To diagnose a problem you need to follow certain steps to eliminate things as being a problem. Guessing at what it might be is not going to get it fixed. You have to get in there and do it.

That said, here is what I would do.
1. If it will crank, crank the car, rev it to about 1500 rpms, disconnect the battery and start loading it like I suggested. This will take 2 people. If it fails while loading it, it's the alternator. If it runs OK then go to step 2. You can usually turn something on and it will start stuttering and when you turn it off it will go away. A car can run on like 8 volts.

2. Connect the battery and do it again. If it fails it's the battery.

That's how I test for the battery/alternator/regulator problems.

That's not to say you don't have another problem like fuel or ignition. When you posted your question it was about an electrical problem. I'm not entirely convinced it is. That's why a mechanic wants you to give them the symptoms of the problem not what you think the problem is. That can lead the mechanic astray.

On a side note I would suggest you adding a signature of what your car is. I know from what you said it is a "96 firebird 5.8L" but that it's. List your modes and stuff.

[Kevin - Blown 95 TA]

Yes it does which is why I said not to use the radio. The radio varies the load a lot where the A/C, headlights, and defroster use a pretty constant flow of electricity.

If you do not disconnect the battery you can not load the alternator. The car doesn't care where it gets it's power from. If the alternator is bad and you have a good battery you will not get the car to fail the test. Since these cars do not have an amp meter you can tell from the dash. A volt meter tells the condition of the battery. An amp meter tells the condition of the alternator.

Not true. Your battery will never show the same voltage if the alternator is running or if it isn't. A voltmeter at the battery is all that is needed to see if it is charging. The current won't be coming from the battery if the alternator is working, because it puts out a higher voltage than the nominal 12.6v, and matter of fact, the alternator will also be putting current right into the battery as well as any other devices running at the time. The battery will charge up from several amps at a tapering rate for about 5 minutes just from starting the car (because it cranks at a few hundred amps for a few seconds) and about 1/2 - 1 1/2 amp thereafter. If the alternator is bad, you will simply be running off of battery voltage which will be lower than 13xxv. Those volt meters in the dash are seldom accurate because of the voltage drop going to them, they are only rough indicators whether or not you have an obvious problem.

You have a good point about the radio, though.

[Jeff_in_Atl]

Not true. Your battery will never show the same voltage if the alternator is running or if it isn't. A voltmeter at the battery is all that is needed to see if it is charging. The current won't be coming from the battery if the alternator is working, because it puts out a higher voltage than the nominal 12.6v, and matter of fact, the alternator will also be putting current right into the battery as well as any other devices running at the time. The battery will charge up from several amps at a tapering rate for about 5 minutes just from starting the car (because it cranks at a few hundred amps for a few seconds) and about 1/2 - 1 1/2 amp thereafter. If the alternator is bad, you will simply be running off of battery voltage which will be lower than 13xxv. Those volt meters in the dash are seldom accurate because of the voltage drop going to them, they are only rough indicators whether or not you have an obvious problem.

You have a good point about the radio, though.

That's not my point. Because the volt meter is so inaccurate you can't tell whether it is charging or not. An amp meter is designed to show whether the alternator is charging or whether it is pulling from the battery. A volt meter can not tell where the volts are coming from. I have seen many batteries that could put out 12 volts and not have enough current to light a light bulb. I have seen a battery with a dead cell that when you put it on a charger it would show full charge and a minute later it would only be charging at a trickle rate. I have also seen a battery that was shorted or something. When it was connected it would make the alternator put out full charge yet it would not power the car. Disconnect the battery and the car ran fine. I hate lead acid batteries. Especially ones built by Exide. Sears Die Hards are built by Exide. Exide's are POS. The leak fumes and make anything aluminum around them corrode. Yea I'm sure not all of them do but every one I've had did.

As for the voltage drop yes you get voltage drop from wire length but it takes a lot of wire to get a voltage drop in DC. In DC you get more current drop than voltage drop per foot of wire. I bet the voltage drop from the battery to the volt meter is less than .1 volts. But I don't want to get into an argument about voltage and current here. I'm just trying to help this guy get his car fixed.

[Kevin - Blown 95 TA]

Jeff, You're a mechanical designer. I'm an electrical engineer working in an ignition and alternator department of a company that makes 13,000,000 engines a year. We know full well how to test alternators. Your last post talks a lot about testing batteries, which is a different subject. A lot of what you said about testing batteries is true, but I was talking specifically about testing alternator output. And most of the voltage drops that happen in cars are from questionable grounds, not wire length. Maybe you should stick to designing mechanical stuff.

[Jeff_in_Atl]

Maybe you should stick to designing mechanical stuff.

That's rather insulting and uncalled for. I also have my ham radio license which requires learning and taking 2 tests about electronics. .....You know this isn't worth it.

[Kevin - Blown 95 TA]

. I also have my ham radio license which requires learning and taking 2 tests about electronics. ......

Well, in that case, I'm going to have to reconsider my opinion

[fastTa]

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.

[Jeff_in_Atl]

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.

Bingo .