[Mgs] fuel gauge and temp

Paul Hunt paul.hunt1 at blueyonder.co.uk
Wed Sep 24 03:54:25 MDT 2008


The Smiths electric temp and fuel gauges *do* rise and fall all the time,
although usually too small to notice unless you look very closely.  If this
were all that were happening I'd say the instrument voltage stabiliser was on
the way out.  But presumably the radio isn't fed from that circuit or it would
always have gone on and off!  In that case it has to be the feed to the radio
and stabiliser that is failing, not the stabiliser itself.  But the other
question is also over the radio, that *should* be connected to a different
circuit altogether - the accessories circuit, which comes on before the
ignition. If it were the fuse the tach would also be going on and off, and all
the other fused ignition circuits like indicators, brake lights, wipers,
heater fan etc.  That leaves a loose connection somewhere between the fusebox
and the radio and stabiliser.  The stabiliser is the last point in a part
daisy-chain and part tree-and-branch structure.  Before that is a branch to
the tach and indicators, and before that the feed to the wiper switch and so
on.  So if the tach isn't going on and off as well I'm tempted to think the
problem *is* with the stabiliser, or its connections.  If the radio really is
going on and off with the temp and fuel gauge then maybe it is picking up its
power from the green at the stabiliser, in which case the problem is at that
connection or the one feeding it from the branch to the tach and indicators,
which is a very difficult to get at multi-way plug behind the dash.

PaulH.

----- Original Message -----


  Went for a 300 mile drive the other day (79B) and noticed the temp and fuel
  gauge were both  rising and falling simultaneously (and the radio was
  working periodically).


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