Volt gauge reading

efnfast · Nov 19, 2024

With the battery fully charged and car (2002 rt/10) on, intercooler pump on, radio on, headlights on (dtrl), radiator fan off, the needle on the volt gauge is just a hair past the 14 mark on the gauge.

Same conditions but now radiator fan on, the volt gauge sits a hair beneath the 14 mark if I'm driving (i.e., RPMs above 1,000), and maybe around 13 if it's idling around 750 RPM (with the headlights being pretty dim until the rpms kick back up).

Is that normal for a Gen 2 whose only additional non-OEM electric load is an intercooler pump? On other cars with a volt gauge usually the needle is well past 14 with everything running and my headlights arn't dimming at idle, so I've been wondering if maybe I should be replacing my alternator?

Old School · Nov 19, 2024

You’re probably right, that’s the classic symptom of diode failure in the alternator.

Goggles Pizano · Nov 23, 2024

Check the voltage. with an actual multimeter. Remember that the voltage regulator is in the PCM not the generator.

MoparMap · Nov 25, 2024

Anything over 13 is ultimately still "good" in the sense that it's providing more voltage than the battery is using. As others have said though, I would check at the alternator and battery terminals themselves to confirm the real numbers (with a good meter I might add, I learned that lesson a while back). The gauge will show whatever the PCM tells it to, not necessarily the "real" number.

efnfast · Nov 26, 2024

I bought Rock Auto's last new mopar gen 2 alternator ... figured cheap and easy enough to try as I don't recall seeing the headlights dim when all the load was on a year or two ago. Or maybe they did and I never noticed it, I dunno, but cheap and easy enough to see.

In my research I did learn about how the voltage regulator is in the PCM ... what engineer thought of that ******* stupidity. God, I hate engineers - like when some Ford engineer decided to re-design how spark plug threads work and figured 3 threads was good enough for Lightnings/03 cobras/etc.

MoparMap · Nov 27, 2024

The regulator in the PCM isn't necessarily that bad of an idea. You get a lot better overall control of the system that way as it can take a lot more info into account. For instance, we have battery temp sensors in our cars that will limit the charge rate of the battery if it starts getting too hot so we don't cook a battery and ruin it. The aftermarket computer on my 5.7 Hemi swapped Dart will let me set one charge rate for the system after startup to get the battery topped back up sooner, then kick down to a lower rate to put less stress on the system. It's a tradeoff, but in my mind a regulator that's not in the alternator itself should be less prone to failure as it's not operating in a dirty environment or around a lot of heat.

efnfast · Nov 27, 2024

MoparMap said:
The regulator in the PCM isn't necessarily that bad of an idea. You get a lot better overall control of the system that way as it can take a lot more info into account. For instance, we have battery temp sensors in our cars that will limit the charge rate of the battery if it starts getting too hot so we don't cook a battery and ruin it. The aftermarket computer on my 5.7 Hemi swapped Dart will let me set one charge rate for the system after startup to get the battery topped back up sooner, then kick down to a lower rate to put less stress on the system. It's a tradeoff, but in my mind a regulator that's not in the alternator itself should be less prone to failure as it's not operating in a dirty environment or around a lot of heat.

Except if it dies in the alternator big deal - $200, 2 bolts, and an hour later you're good to go. Not so cheap or fast if it's the PCM.

Goggles Pizano · Nov 28, 2024

I remember when you could just bolt and unbolt the regulator on the alternator yourself.

Cooking the battery must be a chrysler thing because I am used it regulators on the alternator.

Viper Specialty · Dec 3, 2024

I am leaning towards a alternator diode on this one. Its being controlled, but it cannot supply. Also possible battery temp sensor issue... scan and see what it says.

Volt gauge reading

efnfast

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efnfast

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