voltage question (not spl related)

hi, on my head unit there is a background that i can choose and it tells me my voltage now normal it reads like 13.6 and that seems to be the average but with my dmm i will get 14.2 what seems to cause this difference. and if possable is there any way to keep my voltage up. i already have a HO alt and big 3. i do have like a 3 year old battery under the hood maybe that is the problem? but it read 12.65 when i check it in the morning but i do here that it is good to replace the alternator and the battery and the alternator at the same time and i didn't.

depends on where the HU is reading the voltage ... if it's going thru the fuse block, that may be lowering it

Agreed.

Any voltage reading at the battery between 13.5 and 14.5 volts is considered normal for a vehicle charging system, if the car has 12.65 volts after sitting all night that is considered normal. You don't have to replace the battery when replacing the alternator if the battery is still in good condition. You can get the battery checked by doing what they call a "Load Test" where they put the battery under a high amperage load for a few seconds after it's fully charged and if the voltage doesn't drop below a certain voltage during the test then the battery is fine, if it fails the test then it will need replaced. Chances are your battery is fine and I wouldn't worry about it.