electrical issue

[HAULN-SS]

So, I put a new alternator in my SS tonight, because I thought that was the problem with it dieing on me a couple of times a while back. Started it at the house, and checked the volt meter int he car, and it was reading normal, took it out, and the whole drive it was reading low, so I didn't want to stop because i wasnt sure if the battery was being drained. So my question is does the volt meter tell me what the alternator is putting out, or the battery? Battery, i guess right? Any suggestions to why the meter in the car is reading low? I had the battery tested at advance, but maybe they dont know what the shit they are talking about

[CaptainHenreh]

Is your voltage regulator internal to the alternator or external? Did you check it with an honest to god volt meter or is this a gauge in your car?

[Steve85]

Volt meter should give you the reading of the battery. But, alternator output and battery voltage should be the same while running. A battery will typically read 14.x volts while the car is running. If it's low, either alternator output is low or their is something seriously wrong with the battery.

You replaced the alternator so I would look for voltage TO the alternator. I'm assuming it's an alternator with internal regulator.

[ViPER1313]

Also check all ground points between the motor and battery/chassis for corrosion and replace any fusible links between the alternator and fuse block / battery. The black SHO charged incredibly weakly because the fusible link was 1/2 burnt out and couldn't keep the battery charged.

[HAULN-SS]

It's the meter in the car I was using, because I don't think I have a volt meter..at least not one that gives actual numeric readings. I'm pretty sure it's an internal voltage regulator.

When I first installed it, the guage in the car was reading slightly above "12" which is the middle reading, and when I drove around, it dropped down to 8. When i got home, I turned the car off, and it started it two or three times, and it seemed to have plenty of juice

To check the voltage TO the alternator would I check the wire that runs into the back of it? I will also have to check those links maybe, too.

[ViPER1313]

How many wires are coming out of the alternator? My SHO has 3 - 2 small 12ga wires (one for the idiot light on the dash, one that was hooked up to a fused positive source at the power distribution block to allow the alternator's regulator to "read" the current voltage and adjust power accordingly) and 1 larger 4ga wire that went through a fuseable link to the power distribution block that actually carried the positive charge from the alternator. There is another 2ga wire from the power distribution block that goes to the + on the starter, and from the starter the loop goes back to the + on the battery. The negative on my battery is grounded to the engine block and chassis. The casing of the alternator is negative, and there is the complete charging circuit.

If the MC has a similar setup then you might want to check the starter connections as well - it's common in the SHO world for poor connections at the starter + terminal to cause weak charging.

[HAULN-SS]

Maybe I am onto something.



Adam is this what you were talking about the fusible link there to the starter? This looks like my setup (this is from the haynes manual), however, i swear my charging line from the alternator is going to the negative side.

[Steve85]

The how many wires is a good question. If it's typical GM it should have the big battery wire and a two spade plug on top. Red wire tells the alternator to start charging and blue wire goes to idiot light (and may also be used for volt meter).

And yeah, you're going to want even a cheap craftsman DVOM for stuff like this, to be able to check actual voltage at the battery and so on...

edit; yeah for schematic!

[CaptainHenreh]

You're trusting a gauge from AC Delco circa 1986 to diagnose an electrical problem?

Go get a good volt meter, then come back.

[D_Eclipse9916]

If its actually down to 8 while your driving its a problem with your charging system not your battery. But get a damn volt meter, who doesnt have one of those nowadays? Then again I cant complain down at college I always had to borrow Ryans because I would forget both my voltmeters in NOVA.

[Gs dewd]

If I remeber correctly there is a diode and or a resistor in the insturment cluster that if it goes bad the alt will not charge. Which one it is depends on your gauge package. I believe you have both. The easy way to tell if the alt is charging without a meter is simple. Ready for it? Start the car and remove one of the terminals from the batt. If the car stays running the alt is charging. Why you ask, the battery is there to start the car and keep the memory of the clock and computer. The alt carries the power load after the car is started. With a meter engine off the batt should put out just over 12 volts. With the car running it should be just over 14 volts at the batt. I myself have 2 g-bodys. A 84' MCSS and a 80' Cutlass. So if you need anything let me know.