Alternator / voltage regulator

Chuck

Supporter
Took a nice 40 mile ride this evening. GT is running SO good. But . . . always an issue.

The voltage gauge was locked at 14.5 volts for the entire trip. Never budged below that. Lights on or off, voltage stays the same. It used to settle down to 12.5 to 13 volts after a few miles of driving.

My guess is the voltage regulator is faulty. It is an internal type. But before I pull it out (no small task) just wondering if any other more obvious issues should be considered.

Battery connections are good. Alternator connection (single wire GM type alternator) is good. Battery is an Optima sealed gel battery - which shows 12 volts when the ignition is off and no load.
 
Took a nice 40 mile ride this evening. GT is running SO good. But . . . always an issue.

The voltage gauge was locked at 14.5 volts for the entire trip. Never budged below that. Lights on or off, voltage stays the same. It used to settle down to 12.5 to 13 volts after a few miles of driving.

My guess is the voltage regulator is faulty. It is an internal type. But before I pull it out (no small task) just wondering if any other more obvious issues should be considered.

Battery connections are good. Alternator connection (single wire GM type alternator) is good. Battery is an Optima sealed gel battery - which shows 12 volts when the ignition is off and no load.
you should see 14.5 all the time when the alt. is working. with key on and engine not running you should see 12.6 volts. then start the engine and if you then see 14.5 volts the alternator is working. it takes 13.8v to 14.4 v to charge a lead acid battery. if the alternator is not working you would only see battery voltage 12.6 or lower as the battery is discharging do to power being used to power the cars electrical components.
 

Chuck

Supporter
Lynn:

No doubt the alternator is working.

But once the battery is fully charged, voltage typically drops to around 13 volts. It is not dropping. I don't want to overcharge the battery. Am I missing someting?
 
Lynn:

No doubt the alternator is working.

But once the battery is fully charged, voltage typically drops to around 13 volts. It is not dropping. I don't want to overcharge the battery. Am I missing someting?

A modern automobile has a 12 volt electrical system. A fully charged battery will read about 12.5 volts when the engine is not running. When the engine is running, the charging system takes over so that the voltmeter will read 14 to 14.5 volts and should stay there unless there is a heavy load on the electrical system such as wipers, lights, heater and rear defogger all operating together while the engine is idling at which time the voltage may drop. If the voltage drops below 12.5, it means that the battery is providing some of the current. You may notice that your dash lights dim at this point. If this happens for an extended period, the battery will run down and may not have enough of a charge to start the car after shutting it off. This should never happen with a healthy charging system because as soon as you step on the gas, the charging system will recharge the battery. If the voltage is constantly below 14 volts, you should have the system checked. If the voltage ever goes above 15 volts, there is a problem with the voltage regulator. Have the system checked as soon as possible as this "overcharging" condition can cause damage to your electrical system.
this came from Automotive Charging Systems -  A Short Course on How They Work because I am to lazy to type that much, hope this helps
 

Seymour Snerd

Lifetime Supporter
Took a nice 40 mile ride this evening. GT is running SO good. But . . . always an issue.

The voltage gauge was locked at 14.5 volts for the entire trip. Never budged below that. Lights on or off, voltage stays the same. It used to settle down to 12.5 to 13 volts after a few miles of driving.

My guess is the voltage regulator is faulty.....

Or, the voltage regulator was faulty and is now fixed...?

I assume all these "alternator running" voltages are with the engine running well above idle, right?

IAE, my only concern with your current situation is the health of your Optima (which I assume is an AGM) battery. I have an AGM battery (Powermaster XSPower) who's instructions clearly state it should never be subjected to more than 13.8V. Of course, dash-board Voltmeters aren't necessarily that accurate, so before doing anything about that you should check the voltage with a good quality digital voltmeter.

However, now that I consult the Optima web page I see that it's is considerably more lax in its charging requirements: see http://www.optimabatteries.com/product_support/charging.php#red1
 
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The charging voltage is 14.2v and the charge of the battery determines the flow of current into the battery. Alternator does not monitor current flow only regulate voltage at 14.2v same as a normal battery charger.
 

Seymour Snerd

Lifetime Supporter
The charging voltage is 14.2v and the charge of the battery determines the flow of current into the battery. Alternator does not monitor current flow only regulate voltage at 14.2v same as a normal battery charger.


That's not quite so, depending on your definition of "normal battery charger". See for instance SC-1200A - 12/8/2 Amp Charger/Maintainer/Tester where it's very clear that this charger does in fact "monitor" (better perhaps to say "control") the current flow (aka charge rate).

Also there's nothing special about "14.2". Some alternators have adjustable voltages, and correct operation is usually taken to be something from high 13 to low 14 volt range.
 

Chuck

Supporter
Or, the voltage regulator was faulty and is now fixed...?

Think you may be on to something . . . . .

Did not mention this in my first post, but the alternator belt was loose. Tightened it up. Then noticed the voltage was locked in around 14 volts. Perhaps slippage of the belt was leading to lower voltage that I mistakenly thought was normal? Did not occur to me that a loose belt could cause such an issue (if it did?). Before being tightened, it squealed like a stuffed pig, but only when first started, after which it made no noise. Now that it is tight it makes no nasty sounds at all.

In any event, thanks all for the good info. Bottom line: I will just drive the dang thing and wont' fret the 14 volts showing on the gauge since that is what it is supposed to be !
 
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