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RE: MGB--gas gauge gocrazy

To: mgs <mgs@autox.team.net>, TRIFARI <TRIFARI@aol.com>
Subject: RE: MGB--gas gauge gocrazy
From: Brian McLaughlin <Brian@smtpmail.orcad.com>
Date: Mon, 27 Mar 95 07:29:00 PST
If the MGB sending unit is like my sprite's, it is simply a coil of wire 
wrapped around
a  non-conducting form of some kind.  The float lever slides a copper 
contact
back and forth across the coil.  The coil is a wire that has a certain 
amount
of resistance per unit length.  As the contact slides back and forth, it 
closes
a circuit of varying resistance (exactly like a slot-car hand controller).

The contact sliding back and forth (after years) erodes the wire that it 
slides on.
The "wire-dust" produced can actually short out sections of the coil, or if 
the wire gets worn through completely, the sending unit is shot completely. 
 As the contact
slides from one shorted-out section of the coil to another, the guage will 
"jump".

Try taking the cover off the sending unit and blowing things out a bit. 
 I've done that a
couple of times to revive my fuel guage.

Brian
brian@orcad.com     
'59 bugeye
 ----------
From: TRIFARI
To: mgs
Cc: british-cars
Subject: MGB--gas gauge gocrazy
Date: Monday, March 27, 1995 2:10AM

I have a problem with my 1980 MGB.  The car will only take about $10 wort=
h of
gas before it starts smelling up my garage.  At $10, the gauge shows FULL=
=2E
 It stays there a long while, then goes to half, the drops like a rock to=
 E.
 I realize I probably have a problem with the sending unit and that the
problem will go away if I buy a new one.  I=92m curious, however, if anyo=
ne can
explain WHY this happens.  Thanks for any help.  =


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