How do you check a charging system? with a volt meter.. on the battery, because that's what a charging system is charging...a battery.

Sure you can "do the math" and add a .25 volt correction for all of the connectors going to the guage...but that was not the intent of the design.

 

In most "normal" cars, the alternator and battery are right next to each other, and the primary power distribution is managed close by too. So the voltage drops among the components are very small. A volt meter that reads from any of those main components functionally reads the voltage in all of them. In our cars, the alternator, battery and primary distribution are at opposite corners of the car. There are multiple intermediate connections that were wonderful when the car was built but have deteriorated in the years and miles since. Fix those connections and replace the corroded wiring, and the distances between components will be much less of a factor.

Someone asked how Porsche could have built a car with such poor electrics to drive around Los Angeles in the summertime. I drove mine around L.A. for almost two decades, in summer and in the almost-summer that happens in December and January. The battery ground strap corroded during that time and presented me with one of three electrical issues that functionally stranded me (the others: Battery died during extended garage storage without a maintainer, and the fuel pump relay became weak). I challenge anybody to drive a 20-30 year old car of any vintage, and have only three electrical issues in that time.

So, where do we want to read the system voltage while driving? The gauge as it is and the alternator light together give you enough info to tell you that you have a problem sometime before you are stranded. That's all they are there for.

 

Like I said, he understood automobiles.


It's clear that you're not fully understanding what the meter measures.

Its not the battery.

You also forget age, and corrosion...and...whatever you wanna do man.

 

I think a slick solution to this issue would be to wire the meter to read battery voltage through a momentary switch. Thus you depress this switch to see the battery voltage and release to go back to normal. This way you only will need the the original meter for both readings.

 

 

I like my old Buick were if the charging system has a fault it lights up "GEN."

If a gauge on my 928s does something different, as in "huh. That's odd," I'll put a real meter between the charging post and engine block. Over 13.5 is good. Less than 12 means alternator dead. Between that means "check further" and likely a diode out.

 

I have enjoyed reading this thread; I am having the predictable inaccurate volt gauge reading, HOWEVER, on cold start, the gauge works near perfect?

1/2 hour into a drive, and the dash reading falls to spot 12. volt meter at jump post reads >13.75. after an hour of driving, dash will read at 10?

what might be "heating" up? another thread suggested replacing a resistor behind the pod at the gauge solves the problem, but then someone else posted
that the resistor has nothing to do with the gauge reading?? ?????