Out of curiosity I looked at my gauge when driving 13.9- 14.2 a/c on and off. Battery is almost 4 years according to the date code. I will be buying another battery soon but not just yet. I bought the car approximately 2 months ago and it's been on a tender since I owned it.(2007). The voltage seems to be normal or slightly less( some have 14.5 according to some old posts I looked up) I'm just curious what are you guys voltage readings
Thanks

 

voltage readings SHOULD have nothing to do with the battery.

Before I had my alternator rebuilt due to a bad bearing, my voltage varied from 13.5-14.5. Now it sits rock steady at 14.2-14.5 with new bearings and brushes. I had a brand new battery.

 

Is that with the A/C on? Without the a/c I'm pretty much at 14.1-14.2. I saw it once for a few seconds go to 14.3

 

with or without, doesnt seem to matter.

alternator had 66k miles on it at time of rebuild and the guy said the brushes were just about gone.

 

I have 27k on mine. I still have the original alternator on my old Camry with 155k miles that I gave to my daughter years ago. As I once said before if Toyota would build this car , most of the small problems would not exist.
I believe that with all the advanced electronics in this car it just may have an impact on the alternator. I'll just eventually change the battery because I'm in Florida and the longevity is not there. I will every now and then keep an eye more often on the DIC voltage readings.
Thank you for your comments

 

One of the problems with having a digital voltage readout is that we start looking at tenths of a volt and thinking that they are significant. They are not. There is just no significant difference between 14.3 and 14.1...both are just fine. Unless there is something wrong with a battery internally, it shouldn't have any effect on the running voltage of the system. If you are driving and the system voltage is anything between 13 and 15 volts, everything is fine. In the old days when we had an analog volt gauge, a one volt difference wasn't even visible on the gauge. You might want to get a new battery at some point just out of caution, nothing wrong with that. I did it at six years just because I felt that failure was imminent and I didn't want to get stuck somewhere, but it was still starting the car fine and the running voltage was the same as always. Don't overthink the situation just because you have a digital gauge that reads out in tenths. Thankfully GM didn't make it read out in hundredths...LOL.

 

Lol thank you

 

My 08/73000 miles with head lights and ac on it stays around 13.9.At startup (Daytime) 14.5.

 

As others have said, the voltage readings are not a indication of the condition of the battery. A better way to check the condition is to have it load tested, and if boarder line, replace it, especially in hot climates. Most auto parts stores will perform the load test without charge..

 

FYI, the DIC and analog voltage gauge on the dash is not telling you the voltage to the dash, but instead the voltage to the BCM and ECM only. Hence digital signal is sent from them to the dash and the dash output voltage reading is this signal only.


So when troubling shooting the system, start with with the car idling, and take direct reading off the alternator to start with.

Hence body of the alternator as your ground point, and the terminal on the back under the rubber cap as your positive point for the voltage probe. The voltage reading should be 14.6 volts.

Next, take a reading off the battery terminals. Here, if you should have only a drop of .1 from the alternator direct reading.

Next, use the positive terminal of the engine fuse box as your positive point for the probe on the multi meter, and the alternator body as your negative point for the multi meter reading. Again, should only have about a drop of .1 volt from the direct alternator reading.

If the battery direct reading is lower than the fuse block to alternator ground reading, you have a problem with the ground wire from the battery to the engine block above the starter.

If both the battery and the fuse block readings are way lower than the alternator reading, then the problem is the positive wires through the starter starter solenoid have back connections instead (connection point for the positive wire off the alternator, then the connection positive wire from the battery to the starter as well)

Now once you have all that solve, now check your DCI reading against the alternator direct reading. It's normal to have about a .3v drop between the two (smaller gauge wiring from the fuse block to the ECM/BCM), and if you have more then this, then you have a problem at either the fuse block for the BCM/ECM, or the connectors on the ECM/BCM instead. Hence get to pull the upper fuse block from the lower connector blocks to clean and grease those connections. the fuse U connectors in the fuse block for the fuses, then pull the connectors off the ECM and BCM to clean and grease those connectors). To add, you have a few ground points as well to the car chassis, and need to check them as well.


As for a low alternator reading to begin with (less than 14.6 volts), all is not lost, and most of the time you can pull the alternator apart to clean and check it, to solve the problems yours.

https://www.corvetteforum.com/forums...nator-fix.html

 

I had a new glass mat battery that had an internal short. It heated up one night and started venting gas. Luckily I smelled it and was able to safely remove it. Had it tested and the alt tested, both tested fine at 2 different shops.

About a month later I was in Houston and noticed my Voltage reading had dropped to 13.2 when I had started the car to go home. Yep it overheated again. I was lucky to find a battery store and bought a new one.

I had been keeping an eye on the voltage since the first overheating event. 14.4 to 14.6 all the time. I have a Billet Tech 170 A alt. No problems since going back to a flooded battery.

 

I have heard good things about the Billet Tech alternator. I also read but I do not know if true that the alternators in these cars are marginal because of all the electronics.

 

Great info here- thanks