Date:         Thu, 31 Jan 2002 21:02:27 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Red light rev
Comments: To: Alistair Bell <albell@uvic.ca>
In-Reply-To:  <B87F1D4B.C4D7%albell@uvic.ca>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 07:11 PM 1/31/2002, Alistair Bell wrote:
>I've wondered wether the long (relatively) wire run from the alt to the
>dash, and the (most likely) less than perfect connector just forward of the
>pass. side tail light would contribute enough resistance to raise the
>required "excitation" rpm.

Not much, unless it was a really bad connection.  D+ is fed by 150 ohms in
parallel with the LED circuit (call that 20 ma) which gives a total
available current to ground of about  80+20=100 milliamps at 12.0 volts
(remember you're not charging at this point).  The _Automotive Handbook_
mentioned a 1.2 watt lamp (about 100 ma) as being the minimum size that did
not require a bypass resistor, incidentally, so it seems that VW was
pushing near the recommended minimum current.

Anyway, with effectively 120 ohms in the feed line, you'd need about one
ohm extra to make one per cent difference in the current.  For contrast,
one ohm in the heater blower circuit gives it half-voltage, and one ohm in
the starter circuit would absolutely shut it down (the actual starter, not
the control circuit -- dunno how much that draws).

david


--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"