Date:         Wed, 1 May 2002 08:50:27 -0700
Reply-To:     Bob Whitby <rpwhitby@MINDSPRING.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Bob Whitby <rpwhitby@MINDSPRING.COM>
Subject:      alternator oddness
Content-Type: text/plain; charset="iso-8859-1"

Oh wise list:
Alternator query this time. I'm trying to track down a "surge" at idle, and thought I should check the state of the charging system on the grounds (pun intended) that a weak system will adversly effect the FI. Soooo, I put my voltmeter across the terminals of the battery with engine off. 8.5 volts! Yikes How does the car start in such a state? I dunno, but it does.

Next I start the engine and let it idle. I'm trying to get an output reading at the alternator so I put my one probe on the red terminal on the alternator and the other on a ground. But all I get out of my digital multimeter is gibberish. It is "auto ranging" so it reads in the Mv range, and it keeps going up! Like 2130Mv, or something. I can't get it to sit still long enough to get a reading.

Fine, I sez, and I takes my multimeter to the battery terminals while the engine is idling. There I get a pretty constant 13.8 volts, after some really weird peaks and valleys, like down to 5 volts then back to 10 and up to 13 and so on. Turn the engine off and I can watch the voltage drop on the battery. Goes down in 10ths, slowly but consistently. I can see why in the morning it was so low.

Any guesses based on this crude analysis? Am I doing something wrong at the alternator so I can't get a reading? The car shows no other symptoms of charging system problems, and the surging may not be related at all, but I'm trying to eliminate causes.

Thanks again,
Bob W.