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Re: Weird electrical short burned throttle cable

To: Alex Avery <aavery@rica.net>
Subject: Re: Weird electrical short burned throttle cable
From: "Patrick J. Horne" <horne@cs.utexas.edu>
Date: Thu, 3 May 2001 12:31:13 -0500
Heating due to current flow will produce the most heating at the point of
highest resistance.  The current flow is from the battery negative post to
whatever the battery cable is hooked to, some times the frame, sometimes 
the engine block.  I prefer the engine block.  If it is connected to the frame 
the next path is through the engine ground strap(s) to the engine.
Most of the time the choke and throttle cables will only smoke when the
engine is being started.  The starter needs about 300 Amps of current 
flowing to turn the engine over.  Continuing the current flow, it next
goes to the starter and then to the battery cable back to the Pos. battery
post.

I would guess that your negative battery cable is connected to either 
the frame or body and that there is a poor connection between the engine
and the body.  The throttle and choke cables are connected to both the 
body and the engine and are paths for electrical current flow if there 
isn't a better path available.  Since their "wire size" is much less than
that of the battery cables they drop more voltage, generating a lot of 
heat when high current is flowing through them.

If the battery negative lead is connected directly to the engine block
then you won't be heating the choke and throttle cables, even if the 
engine ground strap(s) are completely missing, unless there is a short
somewhere else between the posative battery lead and a frame or body ground,
which would use the throttle and choke cables as a current return path from
the body/frame to the engine block where the battery ground cable is 
connected.

Make sense?

Peace,
Pat

-- 
- Support Habitat for Humanity, A "hand up", not a "hand out" -

Pat Horne, Network Manager, Shop Supervisor, Future planner
CS Dept, University of Texas, Austin, Tx. 78712 USA 
voice (512)471-9730, fax (512)471-8885, horne@cs.utexas.edu

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