Why is my new 3G alt not charging my batt?

[Mr_Q]

So whenever I key on I am still getting a pathetic 8volt reading on the stock gauge and when I turn it over it dips to like 4 or 5. Then at idle sits dead middle.

I've already had one battery die, was the 4 yrd old cheapo one, and I have replaced it with the new hotness Optima.

I have a new 130amp alt with upgraded wiring so what the hell else is not letting the alt charge the batt correctly???

 

[HISSIN50]

For giggles, I would put a real DMM on there and see what is going on. I have never gotten a car to start with less than about 9 volts while cranking.

If there is a real issue, I would check the wiring over to make sure no connections came loose, etc. I might also look for parasitic loss when the car is off (drains). Dont forget to check the alt as a source of a battery drain (happens when a diode goes south in the alt).

If all pans out and you still seeing low voltage (with a battery that run down, the 3G should be putting out 15 volts or so upon starting up), I might have it bench tested.

Others will have better advice.

Good luck.

 

[rockyracoon]

check the fuse for the alternator, it should be where all your relays are.

 

[04sleeper]

Could you take a picture or elaborate on how you upgraded the wiring?

Did you hook up the excitor wire?

I would also try a good DMM as well just to be sure.

 

[Mr_Q]

okay what's a DMM?

 

[jrichker]

okay what's a DMM?

Digital Multi Meter, same thing as a DVM, or Digital Volt Meter.
DMM's typically have an OHM, AMP and maybe even a Temp scale on a deluxe one like some of the Fluke DMM's
See http://us.fluke.com/usen/products/categorydmm

Fluke meter are very good, but also very expensive. A more modestly priced one from Radio Shack will do fine.

 

[Raginstang]

yeah dude...definetly check the voltage using a DMM. I did the same upgrade you did and had the same thought.. my guages showed the same readings.. I freaked out that I just spend all that money.. I replaced the battery with a optima red top and same thing.. then I finally used a Voltmeter to check it and the thing said 14.5 volts charging... point is.. the stock guage probally isn't that accurate!

p.s. make sure the battery is good in the voltmeter.. once I replaced a alternator because I thought it was overcharging it was showing 16 volts... I finally used an alternate on and got 14.5 volts... found the battery low on the other meter was making it show higher.. just beware!!