IML: 59 fuel gauge problem

[Joe Strickland <jwstrick426@xxxxxxxxxxxxxx>]

From: mtnose@xxxxxxxxxxxxx


My fuel gauge was going all the way to full, so I had my extra sending
unit rebuilt. Got it back put it in and it still reads full. Disconnect
the sending unit gauge goes to empty, no in between. Tested original
sending unit and it gives the same resistance as the rebuilt one 20oms 
to 213 ohms. Checked the volts at the tank end of the wire 12.2v. Still 
reads full or empty when disconnected.

Fred;

You did well in checking the resistance of the sending unit.  You know 
that it is OK.  In all of these cars, the instruments run from a 5 volt 
regulator.  In many of these it is built into the fuel gauge.  In some 
models it is a separate item attached to the back of one of the gauges 
or in some other cases plugged into a circuit board which the gauges are 
mounted to.  When the regulator fails and passes the full 12 volts on to 
the gauges they will read high since they have more than twice the 
normal voltage applied to them.  (The ammeter gauge is an exception to 
the above statement, is is in parallel with current going to/from the 
battery and generator).  All Chrysler products used this 5 volt 
regulator even on the models that operated with a 6 volt electrical 
system (1955 and previous).  You may not be able to see the regulator 
from the outside of the gauge.  Not all of the service manuals discuss 
this fact.  I looked at the '56 service manual on the club website and 
it does not mention this regulator.  It may have been covered in detail 
some years before in either a service manual or in some training material.

Does anyone else in the group have detailed information on which gauge 
has the regulator?

Joe S.


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