Alternator Guage running near Red-Line, help on Diagnosis

[crockman]

I have a 1998 Buick LeSabre. It's Fully Gauged.

The Alternator Gauge normally runs at just over 13. Now that it's got Cold here in Minnesota the Gauge at Times shows much higher than 13.
The Gauge Limit is 18, next number shown is 13, so I'm guessing Red-Line starts around 16 and ends at 18.

On Cold Starts the Gauge shows at a fraction below the Start of Red-Line, 16ish ? It never use to show that high during Summer.

Sometimes it may take hours for it to fall back to just over 13 (the normal shown all Summer)

Some Weird Actions as well:

I deliver Pizza. If I leave the car running at all times, even when inside the Store, if it's been running long enough so the Water Temp gauge gets up to around 200 making the entire car inside and out toasty warm, then the Gauge will drop back to Normal 13ish. When I then go on delivery and the Water Cools, the Alternator Gauge will immediately climb back to Red-Line.

Also, for the First Time a couple days ago, I noticed a very noticeable Dimming of my Headlights, a Glance at the Alternator Gauge showed under-13, was there for only a few seconds then went back above 13 and the Lights re-brightened.

Please help in the Diagnosis of this problem.

Thanks

 

[jlee]

13v is very low for alternator output. Dash gauges don't have the greatest reputation for reliability, so if you are concerned I would put a multimeter across the battery when the car is running and see what the voltage reads there.

 

[bruceb]

Agree with what jlee said. Worst case, is the regulator inside the alternator or maybe the battery is on it's last legs. If the alternator has never been changed, it may be time to do it. Also a lot of stores like PepBoys or Autozone will do a fast on car test of your charging system and let you know if there is an issue.

 

[JCH13]

What's happening here, I bet, is that your engine is idling higher after a cold start (due to the low temperatures) and that's spinning your alternator faster, creating a higher voltage (despite the voltage control hardware on it, there are fluctuations). Idle air control systems/the intake generally let(s) in more air in cold temperatures because (1) more fuel is added to help starts and (2) the air is denser and simply more gets in.

Your symptoms match this:
When you park the car everything gets warm and the idle speed drops as the IAC closes down.
When you drive the car things cool off, and continue to cool off despite the thermostat being shut, so idle climbs back up and thus voltage climbs back up as the IAC opens.

Also, what JLee said: if you're really worried, measure it. Otherwise, I think you're just seeing a funny effect from driving in cold weather.

 

[leper84]

13-14v is pretty standard voltage for an alternator, though the voltage regulator built into your alternator may change this depending on demand. If you go anywhere over 15v (tested with a multimeter at the battery or alternator) you need to change your alternator ASAP.

Sounds to me like the voltage regulator in your alternator is taking a crap. I'd check it out pretty quickly.

 

[dave_the_nerd]

Agree with what jlee said. Worst case, is the regulator inside the alternator or maybe the battery is on it's last legs. If the alternator has never been changed, it may be time to do it. Also a lot of stores like PepBoys or Autozone will do a fast on car test of your charging system and let you know if there is an issue.

+1

 

[freeskier93]

13v is very low for alternator output. Dash gauges don't have the greatest reputation for reliability, so if you are concerned I would put a multimeter across the battery when the car is running and see what the voltage reads there.

I wouldn't consider 13v "very low". Anything over nominal battery voltage (~12.9v) is acceptable.

Also, '98 LeSabre is EFI. OP should verify if the voltage regulator is in the alternator or the ECU/PCM.

 

[jlee]

I wouldn't consider 13v "very low". Anything over nominal battery voltage (~12.6v) is acceptable.

Also, '98 LeSabre is EFI. OP should verify if the voltage regulator is in the alternator or the ECU/PCM.

Source?

http://www.aa1car.com/library/charging_checks.htm

 

[freeskier93]

Source?

http://www.aa1car.com/library/charging_checks.htm

As long as charging voltage is above nominal battery voltage then the battery will charge, and that's really all that matters. That's not to say 13v is abnormally low for that vehicle, but since every vehicle is different it's a general enough statement to be true in every case.

 

[JCH13]

As long as charging voltage is above nominal battery voltage then the battery will charge, and that's really all that matters. That's not to say 13v is abnormally low for that vehicle, but since every vehicle is different it's a general enough statement to be true in every case.

False, good sir.

See: http://www.powerstream.com/SLA.htm

Anything above 2.15 volts per cell will charge a lead acid battery, this is the voltage of the basic chemistry. This also means than nothing below 2.15 volts per cell will do any charging (12.9V for a 12V battery) However, most of the time a higher voltage is used because it forces the charging reaction at a higher rate. Charging at the miminum voltage will take a long long time. As you increase the voltage to get faster charging, the voltage to avoid is the gassing voltage, which limits how high the voltage can go before undesirable chemical reactions take place. The typical charging voltage is between 2.15 volts per cell (12.9 volts for a 6 cell battery) and 2.35 volts per cell (14.1 volts for a 6 cell battery). These voltages are appropriate to apply to a fully charged battery without overcharging or damage. If the battery is not fully charged you can use much higher voltages without damage because the charging reaction takes precedence over any over-charge chemical reactions until the battery is fully charged. This is why a battery charger can operate at 14.4 to 15 volts during the bulk-charge phase of the charge cycle.

Also see:

https://en.wikipedia.org/wiki/Lead–acid_battery#Voltages_for_common_usages
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

The trick here is that while the battery is called a 12V battery, each of the six cells actually rests fully charged at 2.1V. Thus a properly charged 12V battery should be 12.6V, but charging must occur at a higher voltage. 2.15v/cell barely charges a cell, so ~2.2-2.4v/cell is more common. This equates to 13.2v-14.4v. Charging at 2.1v/cell doesn't work because it doesn't fully reverse the electrochemical reaction, if it did then lead-acid batteries would be 100% efficient, and that just isn't possible.

Much over 2.4v and the battery may start to out-gas hydrogen, so seeing a system voltage approach 15V (via good multimeter, not dash gauge) would be concerning.

 

[freeskier93]

False, good sir.

See: http://www.powerstream.com/SLA.htm



Also see:

https://en.wikipedia.org/wiki/Lead–acid_battery#Voltages_for_common_usages
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

The trick here is that while the battery is called a 12V battery, each of the six cells actually rests fully charged at 2.1V. Thus a properly charged 12V battery should be 12.6V, but charging must occur at a higher voltage. 2.15v/cell barely charges a cell, so ~2.2-2.4v/cell is more common. This equates to 13.2v-14.4v. Charging at 2.1v/cell doesn't work because it doesn't fully reverse the electrochemical reaction, if it did then lead-acid batteries would be 100% efficient, and that just isn't possible.

Much over 2.4v and the battery may start to out-gas hydrogen, so seeing a system voltage approach 15V (via good multimeter, not dash gauge) would be concerning.

Fair enough, I'm aware that "12v" lead acid is actually 12.6v didn't know the voltage requirements for charging. As mentioned earlier though the OP should verify with a multimeter what the voltage is at the battery.

If voltage is regulated by the ECU/PCM it's probably using a voltage sense that is the furthest point in the system, which should be about the largest voltage drop in the system. If the gauge is showing around 13v it could be quite a bit higher at the battery.

 

[bruceb]

This link tells how to precisely check the GM alternator used in the 1999 (and other model) LeSabre .. read both page 1 and page 2

http://troubleshootmyvehicle.com/gm/3.8L/how-to-test-the-alternator-1

 

[crockman]

Thanks for All the Replies.

For the easiest possible fix I went to the Local AutoZone Car Parts Retailer and had them test my Battery.

They tested the Battery while still in the Car, it tested Bad. So I bought and replaced the Battery right there in AutoZone's parking lot.

While uninstalling the old Battery I noticed the Bolt (Side-Post) on the Negative Battery Cable acting kind of funny, upon inspection the Bolt was stripped, all the threads were gone. I then bought a new Bolt ($2.50 for 2 of them) there at AutoZone, replaced the Bolt, then installed the new Battery.

Due to the Bolt being stripped I had them retest the old Battery when outside the car, it still tested Bad. So I left the new Battery in.

It's possible the stripped Bolt was causing the problem all along. The Sears Diehard Battery was 5 years old and tested Bad anyway, so I did put in a new Battery.

I haven't driven the Car much to tell if that fixed the problem or not, but being the Bolt was stripped, I'm guessing the problem solved, will let you all know if not

Thanks again