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Re: blowing fuses

To: "MonteMorris" <mmorris@nemr.net>, "MG list" <mgs@autox.team.net>
Subject: Re: blowing fuses
From: Barney Gaylord <barneymg@ntsource.com>
Date: Tue, 18 Jun 2002 01:56:45 -0500
At 01:33 AM 6/18/02 -0500, MonteMorris wrote:
>I keep blowing the bottom fuse on the 67 B, .... How do I go about testing 
>for a short circuit ....

Disconnect all green wires from that fuse.  Switch on ignition.  Touch the 
green wires one at a time to the fuse output.  When the fuse blows you have 
the culprit.  Leave that wire disconnected, reconnect all the others, and 
replace the fuse.  The thing that does not work with that one wire 
disconnected is in the faulty circuit.

Or if you don't want to blow one more fuse, disconnect all green wires from 
that fuse, and check resistance to ground on each one.  When you find one 
with less than one ohm to ground you have it.  It will most likely be a 
dead short showing just about zero ohms.

>Could the voltage stabilizer be causing too much currrent to be passing 
>through?

Only if it's shorted to ground internally.  Otherwise it only passes as 
much current as the devices it powers consume.

>How do I check for, and isolate, a direct short using my multimeter ....

Set it to ohms and use the lowest resistance scale (although many newer 
digital units are auto-ranging).  Touch the test leads together, and it 
should read zero resistance (if not, install a new battery).  Touch one 
lead to any good chassis grounding point and the other lead to the wire in 
question.  If that circuit is shorted it will read zero ohms (or something 
very close to zero equal to the resistance of the copper wire).  You need 
to disconnect and separate all of the green wires at the fuse block when 
you do this so you can tell which wire is causing the problem.

Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg

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