[Vwdiesel] Alternator question

MLightner mikel at buncombe.main.nc.us
Wed Jan 31 19:22:24 EST 2007

>Message: 4
>Date: Tue, 30 Jan 2007 09:14:11 -0500
>From: MWoodland at Dentsply.com
>Subject: [Vwdiesel] Alternator question
>To: vwdiesel at vwfans.com
>	<OF7E5A829F.6DEB88ED-ON85257273.004E0DA0-85257273.004E3486 at dentsply.com>
>Content-Type: text/plain; charset=US-ASCII
>I noticed the lights flickering on my Jetta ('91 NA) last night, and tested
>the voltage at 13+ volts DC charging, and almost 30 volts AC.
>My first guess would be that I lost a diode in the bridge rectifier, which
>is probably inside the alternator, and not part of the voltage regulator..
I agree...

>Haven't yanked it apart yet.
>Does this sound right?
>Any BTDTs?
unfortunately, no, sorry...

>Best regards,
Hi Mark,

I've never thought to check for AC voltage on a bad alternator before, 
but I do know that, even with a bad diode, the the alternator can charge 
the battery while it's running, and then it usually discharges the 
battery while the car is parked.  

I went out and checked my Jetta, and the only place I found any 
significant AC voltage was on the W terminal, and it was somewhat less 
than 10 volts. I also noticed that it is putting out about 14.2 or so, 
as opposed to its usual 13.5, and at first I thought 'hmm, it must have 
gotten stronger', but then I recalled that when the meter's battery 
starts getting low the readings tend to be higher - just thought I'd 
throw that in  ; )


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