Re: Tank Sending unit

[jlandry@domain.elided (John A. Landry)]

LATE BREAKING NEWS: Al Evitts <albert@domain.elided> wins the 40 million
dollar lottery and says:

>Digesters:  What is the compatability of the Sending unit in the gas
>tank and a VDO Fuel guage, if anyone knows.

Al,

Depends on what resistance the VDO gauge is designed to operate with.
Going from memory, the IH sending unit is *supposed* to create something
like 8-10 Ohms when the tank is full and something like 60-80 Ohms when the
tank is empty.  You'll need to check with VDO to see what their gauge
needs.  Autometer makes different gauges to work with all of the standards
out there... so likely VDO does also.

> Also My fuel guage goes
>immediately to full at the turn on of the switch and stays there.  Don't
>that indicate a faulty ground at the sending unit.  Both wires at the
>tank are accessible now, is there any way to check these wires ,if so
>how?

Yes... the gauge pegging out (and the other gauges working more or less
normally) points to the fuel tank sending unit or the wire being grounded
out somehow.  One way to isolate whether or not it's the fuel tank sending
unit is to disconnect (or cut) the wire at or near the tank and using an
Ohm meter, see if you have a resistance reading more or less in line with
the fuel level in the tank.  Again, if the tank is full you should have
about 8-10 Ohms and if empty about 60-80 Ohms.  If the tank level is
somewhere in between, then the reading should likewise be somewhere in
between.  If you have very little resistance, then you know something is
wrong with the sending unit.  If it's fine, then you can start suspecting a
short (to chassis ground) somewhere in the wire lead between the tank and
the gauge.  From there it'll be good old detective work to find it... or
simply run a new wire!

Happy troubleshooting,

John L.
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