Date: Wed, 26 May 2004 22:18:19 -0700
Reply-To: Gerald Masar <azsun99@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Gerald Masar <azsun99@EARTHLINK.NET>
Subject: Re: check for bad alternator
Content-Type: text/plain; charset="iso-8859-1"
Here is some information, courtesy of Doktor Tim:
To proof your battery and charging system follow these steps and skip none
if you don't want to waste money on what it isn't.
1. Verify both ends of both batt cables are clean and tight. Same for the
ground strap at the front tranny mount.
2. Verify the battery top and case is clean and dry.
3. Verify battery is fully charged. You need an accurate VOM for this and
all the following.
4. Turn the key to on then turn on the bright headlights and blowers and
watch as the volts drop to about 12.3v. Then turn everything off and watch
the volts rebound to 12.6+ within a minute or two. If it drops lower than
12.3 within a minute or so, the battery is weak. If it will not rebound to
at least 12.6 it is also weak. If the battery passes this test then you can
use the bucks you would have wasted on replacing a good battery to go to
eBay and buy a quality $200 multimeter for the price of a good extra duty
group 41 battery.
5. Only now are you ready for a test of the alternator. At idle, place one
lead on the batt + and the other on the alt output. If you read more than
1/2 volt you have a problem with resistance in the wiring to the battery.
Recheck the big lug connections at the starter for clean and tight. If you
have less than 1/2volt drop, hook up the multimeter to batt + and - while
idling. Should see 13.8 or so with no other loads. Turn on the brights and
blowers. At idle should not drop below 13.3v. Rev to 2000+ and with the
loads should not be less than 13.5v. Lower numbers say replace the weak
alternator, but before you do, replace the indicator bulb. An old bulb can
have resistance that will not keep the alternator excited.
Over 95% of the time these steps will identify your problem and you won't
waste a cent on good parts. The 5% is related to some very occasional
issues of strange battery behavior. Battery continually tests good but let
it sit for a few days and low charge. I have seen these strange batteries a
few times, and several that were new and had these strange faults from the
get go. If I have truly verified all steps as above and still have issues,
then I will disconnect the battery, put a full charge on it, load test and
watch rebound come back good, then let it rest for several days while
monitoring. If it drops more than a 1/2 volt in a week, then the battery is
weak. A dirty battery top will always fail this test from losses due to
cross cell flow through the dirt/acid conductor all over the case.
Easy squeezy test for cross cell flow. Connect multimeter + to batt +.
Touch multimeter - to various places around the battery top. If you see a
few tenths of a volt, not bad. If you see more than 1 volt, the case is not
clean. I have many times seen 8 to 12 volts cross cell flow on filthy
batteries. This sucks the life out of the battery, alternator and starter
and the continuous loss of amps means everybody must work under much higher
stress. You get no work from those lost amps and you must pay extra in lost
life of components to replace them.
After all these items have been verified and you still have a draw issue,
then begin looking for other items drawing amps in excess.
----- Original Message -----
From: "Ki" <ki@CLOUDFACTORY.ORG>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, May 26, 2004 1:31 PM
Subject: check for bad alternator
> what's a quick way to check to see if my alternator is bad?
