Fuel Sender Compensator

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Original submission by T Feb 27th 2007:
This is a Work In Progress. Details may change at any time as the results
are tallied and the design modified or improved.
==Fuel Sender Compensator:==

What is the Fuel Sender Compensator?

By using the Brass Conductor in the centre of the Fuel Gauge Sender as a Potentiometer for a
sensitive Electronic Amplifier some indication of the level of Fuel in the Tank can be obtained.

The Electronic Amplifier needs significantly less current to determine the Tank's level and can convert this information into enough drive to make the Fuel Gauge read.

Note* this circuit is only for Wagons with dead Senders. On any other model it's easier to simply replace and/or repair the Sender. Certain models work in reverse polarity which is why
this circuit is recommended for HZ.


 The initial design is only intended to provide some indication of the level of Fuel in the
Tank that is accurate about some parameters. This is only intended to be an improvement over the present situation which gives no reading at all. Greater accuracy cannot be provided at this stage. Later designs may increase the accuracy.

Full = Full

1/8 = Anywhere from 1/8 to just under Full

Empty = Anywhere from Empty to just under 1/8

===Improvement in Design:===

A later design may use an Alternating Current and the Capacitance between the Brass Conductor
and the Fuel in the Tank as a dielectric to determine the Fuel Tank Level. The current flow will be very small.

===The Problem:===

On HZ Wagons, and some other models, the original Fuel Tank Sender unit fails. In Sedans these can be replaced through the Boot which is a relatively straight forward job. In a Wagon the Fuel Tank has to be removed first. This is a costly and time consuming job, especially since the replacement Fuel Tank Sender Unit fails soon afterwards anyway.

===Fuel Sender Failure:===

The cause of the failure seems to be the Pivot about which the Float Arm rotates.
The Pivot Arm wears and no longer provides an electrical path for the Fuel Gauge to ground through.

===Fuel Sender Compensator Circuit:===

Image and Circuit Design by T Feb 27th 2007:
It may be argued that the MJ2955 Power transistor is overkill, but I always over-rate
every Electronic component I use in Automotive environments for both reliability and safety

The MJ2955 will reduce the current flow into the Sender by at least a factor of 20.

===Fuel Sender Compensator Wiring:=== On Hz's, the best place to access this is from behind the Driver's Kick Panel. After the Kick
Panel has been removed a large connector with a Lght Brown Wire will be visible.

The Light Brown Wire connects the Fuel Gauge to the Fuel Sender. Cut the Light Brown Wire and
insert the following circuit in there.

Image and Design by T Feb 28th 2007: