What does your volt gage read (gage on far left of cluster)???

Mine appears to read halfway between 13 and 14 - and yours???

About the same - 2004 C2

Mine starts at 14 and drops between 13-14 after a few minutes driving.

Quotes source post: 6856415

Close to 14 on both my 996 and GT3. Looking at a clock face, it would be the hour hand at 9:45-10:00 with no accessories on. Underload, it get's closer to 9:30. -td

9:30 is WAY past beer-o'clock

Follow up question: What does this gauge really indicate? Is it how much voltage the car is currently using, or how much voltage-capacity is still available (net of current usage)? Is the reading taken at the battery or the alternator? Mine is always roughly the same as others have posted above.

Quotes source post: 6856995

Actually neither...it's showing what voltage the electrical supply (battery + alternator) is providing at that moment. You could take it at either the battery or alternator and it would be the same. The voltage varies based on health of battery, health of alternator, engine RPM (assuming it's started), and electrical load at the moment (aka what stuff is on). Voltage drops when system cannot supply the required current needed (aka low RPM, highbeam + rear defroster on). So car off..you should see 12V. Turn on accessories, you may see a drop if battery cannot supply current at 12V. Crank the car, voltage will definitely drop. Once car is started, alternator voltage is higher which lets the battery charge...13.5V to 14.4V (operating range for our cars may be different - have to check). If it goes outside of this range, the alternator and/or battery is getting (or is) bad.

Quotes source post: 6857204

Then if my battery checked at 12.23 volts this morning and my voltmeter reads about 13 - 13.5V, my alternator is probably OK? The read the alternator at 13.3 or something and it was suggested to me that it was on the 'lo' side.

Marlon, If your battery really started at 12.23 V this morning (yesterday, obviously!), your battery is close to being dead. Were you using a good multimeter? (I would not suggest using the dash instrument unless calibrated.) I might have the battery "load-tested" and if it comes out fine, check alternator.

Quotes source post: 6858167

Yes, I used a handheld mulitmeter. Last night it was 12.29. The battery in the car was brand new 2 months ago. Maybe I'll go ahead with my alternator R&R. I notice that the alternator is pretty exposed to the elements - how come there's no 'cover' over it to prevent drenching in rain, etc. I had a 120K mile 99' Range Rover that had to have a new alternator at 90K miles - why? Because the passenger-side windshield washer hose became disconnected from the washer jet and for about 4 months was squirting washer fluid directly on the alternator whenever I used the washer system (about once a week - maybe). (shame on me for not investigating loss of windshield washing ability during that time ). Anyway, the electrical system 'failed' and the cause was: dead alternator. Gotta' be a way to fab a simple cover for the alternator while not affecting cooling air flowing over it and prevent drenching. My guess is that the 996 alternator will last longer. I am going to get some thin sheet aluminum and see if I can fab a tasteful cover during my alternator R&R.

Useless... To be really usefull it needs to be digital or have an even tighter "span", say of only 12-14 volts.

Quotes source post: 6858668

Would not the battery be 'overcharged' at 14 volts? On what kind of car do you find a 14 volt system? Your logic suggests that maybe 15 or 16 volts would be even better?

Marlon: Didn't the reman engine come with a new alternator?

Quotes source post: 6859083

Yes it did - BTW: according to the charging system diagnostic just NOW: my alternator is putting out 13.98V/12.8A NO load and 13.720V/9.6A under load. During cranking the system draws 10.27V/264.7A over 1.78 seconds. The battery is 3 months old and after charging at Advance Auto (for free) it reads 12.84V / 675CCA/rated at 700CCA at 74 degrees. My battery and charging system is fine - whewww~!

Close to 14 for me. Never really moves.

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va bene

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Yes, but the alternator output needed to charge the battery is often above 14 volts, especially in wintertime. A quick check, rule of thumb, is that without the engine running and minimum load on the battery it should read above 12 volts. Start the engine, idle, and the meter should go well above 12 volts. Now turn on both your high and low beams and the voltage should drop slightly but not fully back to the engine not running voltage.

Quotes source post: 6858795

Voltages while driving are not related to the battery, but to the alternator, and should be mid-14s to start, and mid-13s while driving any length of time. If voltage is in the 12V range (or less) while driving, the alternator has failed and is not doing its job. First thing I'd do is check to ensure gauge calibration (not to mention eyeball interpolation; 9:30 isn't a voltage measurement!) by using a multimeter to check this voltage at the battery terminals with a multimeter while the car is running- check the battery before and right after start, and again before you turn the car off after driving it. This is all related to charging on a 12V system, and extending battery life. 14V is fine for the battery for short durations. 15-16V is overcharging it and would rather quickly drive off water and harm the cells. As the car sits, the battery is constantly in-use for the security system, the keyless entry, running the radio clock, etc. Not a whole lot, but it all can add up. Whenever you start the car, the starter consumes a really big chunk of electricity from the battery. The battery will continue to have usable energy until it drops below 10V in which case don't even bother trying to recharge it, just go get a new one. When you start the car, the alternator ramps up to a fast-charge of about 14.5V for a short period to recharge this as quickly as possible. If the alternator maintained this voltage all the time, it would overcharge and decrease battery life, so the alternator will ramp down after a few minutes to about 13.5V float charge (or trickle charge) level, which is a safe voltage to always keep the batteries at while charging. Same is true of plug-in battery chargers/battery maintainers. When you stop the car, the batteries will slowly creep back down to their natural voltage of somewhere around 12.0-12.8V, depending on age/condition. At voltages under 12.5V, sulfation can form, which hurts the battery and reduces cranking amps. It's a slow growth that occurs over time. It largely all dissolves when a higher float voltage is applied to recharge it, but sulfation is an insulator, and if it grows large enough, it can completely choke off a cell and result in a dead battery. A good new battery with a full charge has a shelf life of about 6 months before irreparable harm is done; older batteries... not so long. My battery right now is sitting at 12.15V, which is awfully low. So long as I continue to drive it regularly to drive off the sulfation, it will keep starting the car, but if I'd let the car sit for a month, I have no doubt it'd be dead. I know I should replace it before it locks me out of the frunk, but I keep procrastinating. The surface of the electrodes in a car battery are a very complex waffle sort of pattern, designed to maximize surface area, and give maximum cold cranking amps, but is rather fragile. Every time you deep cycle the battery, you damage these structures a little. Too many, and you can just throw the battery away. Deep cycle marine batteries and UPS batteries use a different electrode design, a more simple one that's thicker and gives less cranking amps, but longer life; these can last for hundreds of deep cycles.

Just got back from a drive and the top of my needle for that gauge sits at the bottom of the hash "---" mark for 14.

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Google works great doesn't it

Quotes source post: 6860841

That was all off the top of my head, actually, I'm an EE and work a lot with batteries in industrial applications and thought I'd share some detail with ya'll. Batteries are often misunderstood and mistreated. Speaking of which, heat is a real killer- for the cheap sealed VRLA batteries everyone uses these days, every 15F over 77F will cut the life in half. At least Porsche put the battery in a cool location for a change, most cars throw them right in the hottest part of the car, which always struck me as incredible stupid. Especially when it *could* go in the trunk and improve weight distribution, too.