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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