Hello

My voltage gage suddenly showes only 10 volts.
Battery is 1 year old with good conections.
Belt is not slipping.

The subject is not addressed in the factory manual. So hopefully someone can help.

Thank you
Yellow

Check the grounds first (especially the engine to chassis one). If they all check out, then have the alternator tested.

Do you have a voltmeter? You can use it to check what the actual voltage is at the battery and see if it matches the gauge.

I have also read about checking the voltage at the battery but I have a question.
Does the voltage gauge actually read what the alternator is putting out or the actual voltage of the battery?
Because, if the alternator was only putting out 10 volts but you have a new battery that has 12 volts what is the meter going to read?

quote Originally posted by TXGOOD: I have also read about checking the voltage at the battery but I have a question. Does the voltage gauge actually read what the alternator is putting out or the actual voltage of the battery? Because, if the alternator was only putting out 10 volts but you have a new battery that has 12 volts what is the meter going to read?

That's a good one.
Even a weak battery reads 12 volts. If the altinator really is putting out 10 volts....where is the missing 2 volts..??

Yellow

quote Originally posted by TXGOOD: I have also read about checking the voltage at the battery but I have a question. Does the voltage gauge actually read what the alternator is putting out or the actual voltage of the battery? Because, if the alternator was only putting out 10 volts but you have a new battery that has 12 volts what is the meter going to read?

I believe the whole system should be operating at about the same voltage, if one portion was significantly higher than another, something is going wrong. I picture that as a fishtank, where one side of the tank is somehow overflowing with water and the other side is low, even though the tank is perfectly level. Filling the tank from one side should quickly spread to the rest of the tank. With the car running with a bad alternator, the battery would be draining to support all the electrical systems and read below the 12 even though it may read normal with the engine off and no load.

My ideas are based only on my own experience and diagnoses of my cars however, not an intimate understanding of electronics.

quote Originally posted by Xanth: Do you have a voltmeter? You can use it to check what the actual voltage is at the battery and see if it matches the gauge.

The battery reads 12 volts. (11.92) The gage used to allways read around 13 V while running. But I've never read a battery with the gage reading 13 volts. Has anyone done that? What sould battery voltage be with everything running normally?

Yellow

I have not measured mine at the battery with a meter but I know that when I first start my car, the gauge reads about 14 volts but after a bit it will drop to 12-13 volts.
With the AC on it drops a little below that and when I turn the blinkers on it pulses with them.
I was always under the impression that an amp meter will drop as the battery gets charged but I always thought the voltage is suppose to stay about the same as the car is running.
I also don`t like the gauge dipping in rhythm to the blinkers being on, but it doesn`t seem to have any affect to the charging system working.

If the battery reads 12 volts with the engine running, check the belt, and battery & alternator connections. If all are good, take the alt in to have it tested as it is most likely bad.

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87 NB, 3800SC, 4T65E-HD, HP Tuners, 13.10 at 102.5 1/4 mile, Custom Dash.

The Gauge, with the key ON, engine NOT running, will tell you what the battery is. Running, it "Should" tell you what the alt is putting out. I think.

Thank you.

Everybody has pretty much confermed what makes the most sence.
All electricity is connected. My altinator is making some, but not enough of it...or it's having troble getting through a connection.
I'll take a real good look at everything tonight but I do suspect something in the regulator pack.

( I still have a spare dynamo and voltage regulator on the shelf from the old days. Maybe........No. )

Yellow

A good 12 volt battery will hold anything above like 11.5 volts after sitting. A fresh fully charged one will show anywhere from 12-13.3 volts (it will drop off a little after it sets a little while. If your voltmeter is connected and car is not running, you will show battery voltage. If its running you will see what alt is charging. Usually anywhere from 13.5-16 volts. 10 volts showing running or not is not enough. If your battery is good, and wiring is good, alt or regulator (integral) is bad.

I have had this problem before on other vehicles. With the engine running you should have about 13-14 volts with the test leads touched to the battery post, not just the clamp. It was less on the post, I took the clamps off and cleaned them really well and coated them with vaseline then reclamped them and coated the post with vaseline also. After that it was charging 13.5 volts. If after cleaning you do not get 13-14 volts then I would have the alternator checked.

[This message has been edited by mickeyswing52 (edited 09-26-2011).]