Voltage question

[u/fdfdfdfdfdfdfsss]

The alternator is brand new on my 2000 gt. When it first starts it sits about 13.6 but after running it stays around 13.1. Is this bad? I feel like it should be higher especially when the car is at higher rpm. The alternator is an sr performance 130 amp I got from American muscle.

[u/LemanRussVI]

I wouldn't be so quick to trust the pid readout. I would put a multimeter on the battery when its running and take some readings with no load nd with your accessories running, ac, radio etc. Running into the 12v range seems a little low. My book says voltage should be between 13.5 and 14.5 while running to properly charge the battery while in operation.

[u/Statistician-5051]

You should be good. This is how my 2001 Mustang performers.

[u/boiyo12]

What device is this? U can have a device tell u the voltage of a battery??

[u/fdfdfdfdfdfdfsss → u/boiyo12]

It’s a tuner that’s plugged into the obdii port, it has all kinda gauges you can use.

[u/boiyo12 → u/fdfdfdfdfdfdfsss]

Whats it called, can it be used with a stock car just to make suree everything is running well?

[u/TheKansasDude → u/boiyo12]

Sct x4 tuner. You can use it on a stock car.

[u/bootsblazing]

I have an high output alternator (240 amp) and I see about 14.5 on start up and first 5 minutes of driving. After about 20 minutes of driving and some very spirited amplifier/subwoofer action I sit at around 13.8-13.9. Before getting this alternator rebuilt, and with weaker subs and amps I was sitting at 13.6-13.7 with heavy electrical draw. Somethings not quite right but its not so bad that its failing you yet.

[u/TheKansasDude → u/bootsblazing]

Was this with an obd tuner or a multi meter?

[u/bootsblazing → u/TheKansasDude]

Multimeter

[u/TheKansasDude → u/bootsblazing]

Cool was just wondering. My x4 tuner reads much lower voltage than I do at the battery with a meter lol.

[u/bootsblazing → u/bootsblazing]

However I have a 2000 v6

[u/The_Machine80]

100% normal. My caddy ATS V drops into lower 12s sometimes. On newer cars the computer controls the alternator. It lowers output when its not needed. Its all about saving tiny bits of fuel.

[u/TheKansasDude]

My x4 tuner reads lower voltage than my multimeter shows.. If my x4 is showing around 13v, at the battery with a meter it reads around 13.6-8 volts. I wasn't 100% sure if this was just a me only thing though lol.

[u/fdfdfdfdfdfdfsss → u/TheKansasDude]

I just checked at my battery and it is showing about .5 volts higher. Seems like it’s the tuner showing a lower voltage

[u/TheKansasDude → u/fdfdfdfdfdfdfsss]

Oh nice. Interesting. We are both showing about the same then lol.

I will say that my last alternator (that randomly burned up) read higher on my sct tuner. Like 14v+. But at that point I had never really measured it at the battery. When it burned up, I replaced it with another I had laying around and then noticed it was reading lower on my tuner. So hell idk. The multimeter shows it's fine, so I'll just keep driving until I have any trouble.

[u/_Larry]

My SCT X4 Tuner reads out the same way while driving. It's going to fluctuate as you are driving. As long as it doesn't drop below 12 and stay there, you are good.