Voltage question (Page 3/3)
1985 Fiero GT OCT 12, 01:11 PM
Ok. My volts are measured by the volt meter which is wired into the ignition switched power and ground on the rear defrost connector, voltage across my while car is relatively stable, like I said the wiring seems good, probably just one connector somewhere that has a problem, I just did a half hour drive with no accessories on, in cool weather and the alternator didn't cut out, voltage started around 12v engine off, 14.3 volts just started up, then dropped to an average of 13.6, jumping between 13.3 and 14, occasionally.
Frenchrafe OCT 12, 05:06 PM
Do you have a multimeter? You should check what the battery is getting. If it's not 14.1V , 14.2V or near then you need to check the output at the alternator +ve wire.
Ditto, if it's not above 14V, then there's a problem.
Less than 14.1 or 14.2V, the alternator or it's regulator is toast.

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[This message has been edited by Frenchrafe (edited 10-12-2023).]

1985 Fiero GT OCT 12, 05:09 PM
Ok, I will check that when I get home, will also compare battery direct readings to my cabin voltmeter to see how much of a voltage drop there is between the battery and the rear defrost switch
Patrick OCT 12, 05:24 PM

quote
Originally posted by Frenchrafe:

Do you have a multimeter? You should check what the battery is getting. If it's not 14.1V , 14.2V or near then you need to check the output at the alternator +ve wire.



On my vehicles, (Fieros and a Subie), 14.6 volts is what my alternator is feeding my battery after the engine starts. A fully charged battery should be just under 12.6 volts.

I also wanted to add, that prior to replacing my alternator two years ago... the alternator would intermittently stop charging and then start charging again. I couldn't trust it. I took it apart to make sure the brushes were making contact etc, but I couldn't visually find any problem. Replacement of the alternator solved the problem.

[This message has been edited by Patrick (edited 10-12-2023).]

1985 Fiero GT OCT 12, 07:51 PM
Ok, I will check that when I get home, will also compare battery direct readings to my cabin voltmeter to see how much of a voltage drop there is between the battery and the rear defrost switch
1985 Fiero GT OCT 12, 08:11 PM
Ok, starting Fiero with multimeter in battery directly, multimeter reads 14.0, volt gauge in cabin reads 13.8, but that is immediately after starting it with no accessories on. After driving it, like I said volt gauge settled to an average of 13.6, which would theoretically put battery voltage at 13.8, still to low, and that is the average, with it varying as low as 13.2 on the gauge (theoretical 13.4 battery voltage) and then the times that the alternator "stops" charging, voltage starts at 11.8 gauge, then slowly drops until it kicks back in, back up to 13.6 gauge
1985 Fiero GT OCT 12, 08:28 PM
Voltage at the alternator is within .01v of voltage at battery when engine is off, 12.42 battery, 12.41/2 alternator, and this time I started it voltage was 14.21v to 14.25v at alternator and battery (voltage varied over the time, wouldn't remain constant enough to check between alternator and battery) for the minute or so I had it on,
1985 Fiero GT OCT 12, 08:34 PM
So it does vary a lot, from selling to be perfectly fine, to simply not working
ZaraSpOOk OCT 12, 08:39 PM
On my 88 V6 the thing that makes the voltage drop is when I first turn on the AC, then it jumps back up. I don't know if it jumps back to what it says before turning AC on because I've never looked at it that close. IMO, if it says 13 1/2 or more I'm not concerned. BTW, I have factory volt meter. In fact I wouldn't be concerned if it said 13 or more because who knows how accurate the factory gauge is given the accuracy of the fuel gauge for example.
Having said that, my gauge the other day started registering a little over 12V and the idiot light comes on and stays on, so I'm thinking new alternator time.
I don't know what all the conversation about different ALT is about, I don't know what the abbreveations you are using means.
1985 Fiero GT OCT 12, 08:42 PM
Long story short, 85/86 fiero's have one, older, worse alternator, 87/88 has The cs130, better newer, etc. Newer alternator can be put in older car, with a simple cable adapter from Rodney