-- [ From: Bob Nogueira * EMC.Ver #3.1a ] --
William:
Very good method for adjusting the fuel gauge but with all that
Ohm, resistors, and one-half Watt 1% stuff your Jaguar breeding is showing
. Hell this is Morgan, We talk angle iron and hammers :)
A method that I have used, and I'm sure will work for other electrically
challenged owners is as follows :
Remove the sending unit from the tank . Place the mounting plate of the
sending unit on the top edge of a piece of poster board .(Note : if you
don't have poster board around the house borrow a seven year old with a
school project for a couple of days and you will find you have an unending
supply )
Measure the depth of the tank at the mounting hole and mark it off from the
top of the poster board, which is 11 inches if I remember correctly . Now
the 11 inch line is the bottom of the tank and the top of the poster board
is the top. Since all the sides of the the Morgan gas tank are
perpendicular to each other ( ie basically a box) 5 1/2 inches up from the
11 inch line is halve a tank. Place the float on the top o the 51/2 inch
line and the gauge should read 1/2 . You can then adjust the magnets to read
correctly.
A WARNING : the wire windings of the magnets is very very fine wire and if
the magnet nut is loosened too much the magnet can turn and break the wire.
Be careful to loosen the nut only enough to slide the magnet . You can see a
piece of plastic ( or something) that is fitted to the slot . to keep the
magnet from turning. If you loosen up the nut more than the thickness of the
metal casing the magnet can turn.
( Does the above sound like a guy who has learned how to solder fine wire ?)
Bob Nogueira 'Who knows his way around school supplies but is
lost in Radio Shack '
PS Be sure to return the poster board to the kid, after all Science Fair
season is just around the corner !
------- REPLY, Original message follows --------
> Date: Wednesday, 08-Dec-99 03:18 PM
>
> From: William Eastman \ Internet: (william.eastman@medtronic.
com)
> To: MORGANS \ Internet: (morgans@autox.team.net)
>
> Subject: Fuel gauge calibration
>
> A couple of people asked for the details on calibrating the old,
differential
> magnet-type fuel gauges. Here is what I did when calibrating a friend's
gauge
> for his MGA. I checked the results on my three Jaguar gauges so I am
pretty
> sure that it is correct.
>
> Go to Radio Shack or some other electronic's store and pick up a sleeve of
five
> 15 Ohm resistors and an alligator clip. Go home and solder them together
in
> series and attach the gator clip to one end. If you can, it is nice to
have a
> short wire with a connector attached to the two fuel gauge leads. This
will
> reduce the chance of shorting everything out.
>
> I used a battery charger for a 12 volt supply- polarity doesn't seem to
matter.
> Hook the 12 volts to the gauge input and the case. Hook the gator clamp
on
> the resistors to the case as well- my gauges have two mounting tangs that
make
> this easy.
>
> The gauge will swing hard past full with the sender wire open and empty
with it
> grounded. On the sender, full gives about 70 ohms resistance to ground so
just
> work down the resistor array from the end to the gator clip for 75, 60, 45
, 30,
> 15, and 0 Ohms to ground. 45 and thirty should bracket the half full mark
with
> the others near the quarter marks.
>
> If your gauge does this, you are done. To adjust, ground the sender wire
then
> loosen the nut on one of the two magnet cores- doesn't really matter
which
> one. Move the core back and forth until the needle points at empty or
just
> below empty- you don't want it above empty or else you will have a false
sense
> of security. Then move to the other end of the resistor array and adjust
the
> other magnet until the gauge points at full or just past full. This is an
> iterative process. Once you are satisfied with the endpoints, check the
middle
> points again to see if they make sense then install and enjoy!
>
> I think the resistors I bought were one-half Watt 1% resistors but I
expect the
> 1/4 Watt 5% resistors would work as well. The sleeve of five resistors
was 99
> cents at the mall. I bought them while my eldest daughter was doing
whatever
> 14 year old girls do in malls when they know their parents may be watching
.
>
> If this is unclear, I can try again. Once you have the parts in front of
you,
> it will make a lot more sense.
>
> Happy Holidays,
> Bill Eastman
-------- REPLY, End of original message --------
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