Cascade Crew

kutison · Posted: Tue Aug 30, 2011 5:40 pm Post subject: Dash gauge reads weak voltage.

I've noticed the needle has been slowly been dropping. On the way back from Vancouver I looked down and noticed the reading was down in red. I

am embarrased for not knowing much about the purpose of this gauge, but it's a measurement of how many volts the alternator is putting out right? And this would mean that the alternator has quit doing it's job?

How would I go about diagnosing that it is indeed the alternator?

Al Hasse · Posted: Tue Aug 30, 2011 6:20 pm Post subject:

That is the basic purpose of the gauge. Do you have a multimeter? If so, take a voltage reading of the battery with the engine off, and another with the engine running. Engine off should read somewhere close to 12 volts DC, mine is 12.5. Engine running should be about 14 volts DC if your alternator is charging the battery.

If indeed your alternator is bad, have your battery checked as well. Parts store can check both for you.

kutison · Posted: Tue Aug 30, 2011 7:58 pm Post subject:

Nope, no multimeter, but I've needed one for awhile. I'm currently broke so I guess the car is going to be sitting. Battery is ~ 1 1/2 years old, alternator is 4-5 from what I've been told.

Thanks for the info

aaron_sK · Posted: Tue Aug 30, 2011 8:26 pm Post subject:

Battery and alt tests are free. Just pull both and have them tested.

kutison · Posted: Wed Aug 31, 2011 6:01 pm Post subject:

Got a multimeter, Car reads 12.4 off and 11.84 running. Assuming I used this new fangled piece of technology correctly.

turbo_jimi · Posted: Wed Aug 31, 2011 6:03 pm Post subject:

did you set the voltage to 20?

kutison · Posted: Wed Aug 31, 2011 6:07 pm Post subject:

yup, I just worry about the quality of the reading because I couldn't leave the needles connected on my stupid sidewall batteries.

turbo_jimi · Posted: Wed Aug 31, 2011 6:18 pm Post subject:

you shouldn't have to leave them there any length of time...your reading are indicating battery drain...bad alt...automotive parts store should test and confirm.

kutison · Posted: Wed Aug 31, 2011 7:14 pm Post subject:

It sounded like the battery was dying as the car was running because the idle dropped significantly as i was testing. This may have just been due to the car warming up though.

turbo_jimi · Posted: Wed Aug 31, 2011 7:16 pm Post subject:

might have the battery tested too...bad alt could be slowly killing the battery.

Alphius · Posted: Thu Sep 01, 2011 9:40 am Post subject:

I had a jeep once that had about 12.4v with the engine off, but anytime it was running the voltage was about 10.8v. New battery and a new alternator didn't fix the problem, I didn't troubleshoot too much since I was just flipping it. It never killed the battery but the "Oh God Something Is Horribly Wrong With Your Charging System" light on the dash was forever dimly gleaming.

TLDR: I am of no help, but have an anecdotal similar story.

For Real Answer: Sounds like the alternator if that hasn't already been replaced.

iansane · Posted: Thu Sep 01, 2011 9:46 am Post subject:

Or the wiring to the alt.

Twilightoptics · Posted: Thu Sep 01, 2011 11:29 am Post subject:

If everything was cool, and now your voltage at battery with engine running is less than with the engine not running.... Your alternator is dead, or a cable fell off/is loose. Check the main lead and the plug at the alternator. If they are tight, free of corrosion, and not loose.... and the battery cables are the same way..... replace the alternator.

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

All grounds good??

kutison · Posted: Fri Sep 02, 2011 9:30 am Post subject:

They seem to be. Alternator is off, now I'm just trying to bum a ride to the parts store for testing.

kutison · Posted: Sat Oct 15, 2011 5:04 pm Post subject:

So i took the alternator to NAPA, the alternator tested fine. When I reinstalled it after a good terminal cleaning and using dielectric grease, it worked fine. for about a week.

Now I am having the same problem. this time the alternator tested good at NAPA, but bad at Knects. I reinstalled it again, but my luck didn't hold.

So now I'm probably going to be replacing the alternator it seems. I just wish the tests had come to a consensus so I could be sure the alternator is the culprit.

iansane · Posted: Sat Oct 15, 2011 5:45 pm Post subject:

Did they tell you what kind of output load on/off, diode ripple, etc it had?

kutison · Posted: Sat Oct 15, 2011 5:55 pm Post subject:

no, knects just said that it was putting out around 5 volts. Napa said it passed, which means, according to them, at least 13.5 volts.

chevymad · Posted: Sat Oct 15, 2011 6:37 pm Post subject:

You have an intermittant problem.. Sometimes its working sometimes it isnt. Thus.. if they check it and its working it tests good.

kutison · Posted: Mon Oct 17, 2011 10:41 pm Post subject:

So bought a new alternator, the car still not charging. 12.6 with the car off. 12.45 running, slowly dropping. 12.33 with lights and fan on.

So if I am reading these numbers correctly, that battery isn't getting a charge.

Is it possible that if my 2 year old battery won't take a charge, and because of it, is frying my alternator? Should I replace my battery and alternator at the same time?

And the voltage regulator is within the alternator, meaning that the whole unit must be replaced right?