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Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection
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TOPIC: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection

Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2795

  • YLG80
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Here is the description of a very damaged fuel gauge restoration.
This is a "paint can" Stewart Warner 6V 400507 fuel gauge.
I've received that gauge from Adam (G503).
Adam wanted to challenge me.

The gauge arrived already opened :
* the face plate was blank and completely deformed. (by heat ?)
* The pointer/needle was missing.
* The bezel ring was damaged by a sharp screw driver blade
* the gauge cover/ring was deformed but the glass was intact and in good shape.
* the mechanism was very dusty but looked still functional which was easily verified.

Yess, the pivot was turning when connecting the gauge to a 6V source!

sw_paintcan-before-restoration.jpg


The deformed face plate removed

deformed_face-plate.jpg



parts.JPG


./..
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2796

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I've printed new face plate decals.
I've designed that face plate with Corel Draw a few years ago when I've restored another paint can gauge found in Luxembourg.
Thanks to the detailed photos published by Chuck Lutz on G503, I've remarked that my design was missing the bottom STEWART WARNER 400507 MADE IN USA identification.
I've added that text to the bottom of the face plate.
The height of the text below has been slightly reduced before printing.

I usually print the decal twice.
This is the decal:

pc-fuel-gauge-face-plate.png


The gauge is of that type, with only one needle peg. So I've patched the other mark for the second peg.

damaged_needle.jpg


After printing the decals with an inkjet printer (old excellent and reliable HP PhotoSmart 1000), we must spray a thick layer of varnish over the printed area.
This will improve the mechanical and U.V resistance of the decal.
./..
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2797

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I've cut the new flat face plate in a piece of double sided printed board of 0.8mm thickness.(fiber glass)
This is a much more stable material than the original zinc plate.
The holes for the rivet, the peg and the needle will be drilled before applying the decal in order not to damage the decal.

cutting-face-plate.jpg


The face plate made form PCB is painted in black before applying the decal.
Now the face plate parts are ready

two-decals-and-face-plate-ready.JPG


Note the straightened and painted housing above the face plate decals

To finish the preparation of the necessary parts, I've also cut two gaskets for the glass. (from a gasket material sheet)


gaskets.jpg

./..
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2798

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It was time to build a new needle.
I've measured the needle length from a picture published by Chuck Lutz on G503.

To evaluate the other dimension I've build a mock up needle and I've found the following dimensions:

pointer_DIY.JPG


I found a very light material to make the new needle : a beer can !

needle-materia.JPG


The needle was cut with a sharp knife, Exacto type.

needle-cut_from_beer-can_material.JPG


The mock up and the needle

IMG_9026small.JPG


The needle attached and glued with UV cyanoacrylate gel.

pointer-needle.JPG
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2799

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The needle and the pivot are reassembled and the assembly is tested by tilting the gauge.
The pointer is moving freely from EMPTY to FULL. It looks good.
I've then varnished the two coils against moisture.

sw_fuel_gauge_no_post_effect.jpg


It's time to electrically test the gauge.
The face plate is attached with two screws for the electrical test

gauge-in-test.JPG
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2800

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The electrical test on my workbench is shown in that short movie :
There is also a demonstration of the dual coil gauge stability against voltage variations.
From 6V to 15V the needle is only very slightly moving.



Here is how to wire the gauge with the sender (potentiometer) and the power supply or 4 X 1.5V (AA, LR14 or LR20 batteries )
If you use batteries don't forget that this type of gauge draws up to 300mA current when displaying FULL.
Disconnect the battery after testing.
The pot used in the video is a 100 ohm because it was the only one I had on hand.
To correctly test the gauge, it's better to use a 150 ohms pot.
Once everything is connected, fully rotate the potentiometer so that gauge displays FULL.
Then rotate the potentiometer in the other direction until the needle touches the stopper.
Measure the potentiometer resistance.
It should be 50 to 70 ohms because the pot is 150 ohm instead of 130 ohms which is the sender resistance.
The residual sender resistance when the tank is empty is not 0 ohm but 10-20 ohms.


DO NOT FORGET (as I did first) TO CONNECT THE GAUGE HOUSING TO THE GROUND !


STEWART WARNER FUEL GAUGE SCHEMATIC
TEST_SCHEMATIC-small.jpg


WILLYS MB AUTOLITE FUEL GAUGE SCHEMATIC
TEST_SCHEMATIC-WILLYS-MB_small.jpg



That configuration can be used with all dual coils gauges and of course you can test your gauge still in the housing..

The dual coil gauge is easy to recognize.
Tilt the gauge from the vertical (like in the dash) to beyond horizontal and the needle moves from EMPTY to FULL and vice versa.
With a single coil gauge, the needle will stick to EMPTY.


At first the needle could not reach the FULL mark.
I had to slightly bend the magnetic blade until the pointer was just in front of the FULL mark.
That blade may also be used to adjust the EMPTY reading.
You need to alternately verify the full needle coarse when you adjust the blade.
The blade is shown at the end of the red arrow on the next photo.

sw_fuel_gauge_bending-blade.jpg




Here is the schematic showing the two coils and the connections in the jeep through the IGNition switch and the tank sender.


fuel_gauge-schematic.png



Once in your jeep, if you have the following problems:
Fuel gauge stuck on EMPTY :
If you have a dirty or intermittent ground connection at the sender unit, your gauge will jump around or be permanently stuck on EMPTY.

Fuel gauge stuck on FULL:
If your gauge is permanently stuck on the full mark it most likely is not making electrical contact with the dash panel .
A clean metal to metal contact between the gauge body and dash panel is needed to provide a current path for coil B to ground at X (body ground) on the circuit shown above .
May be some paint or rust is causing a intermittent path to ground at X (housing)
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2801

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Something to know when repairing the Willys MB gauge (Autolite).
There are often contact problems due to the oxidation.
You have to pay attention to the location pointed by the red arrows on the next picture.
There are sometimes no contact between the soldering eyelet and the post or between the brass surface and the rivet.
Double check the contact between each pair of red arrows.
If the contact is not perfect, clean the area with your Dremel (wire brush) and jump solder the post and the eyelet edge with tin solder.
(Use non corrosive flux and remove the flux residues after soldering)

Contact-problem.jpg


See the example on the center ground brass rivet.
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2802

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One of the most common cause of problems with this type of gauge is poor grounding.

The dual coil gauge is a one wire gauge (that's a claim in the original patent), but obviously there is a second "invisible" wire : the Jeep body (ground)
You can see the ground path in green on the next wiring diagram :


fuel_gauge-ground-path.jpg




The green dotted lines is the ground path through the jeep body.

You need to bee sure that the sender is correctly attached to the tank, with no oxidation.
The tank itself is grounded via the output pipe.

The gauge has to be grounded via the gauge housing and the dash board. Remove and oxidation and paint from the dash hole and remove paint behind the dash where the U holder
will be in contact with the dash.

These precautions will avoid the usual problem of the "fool needle" always jumping from EMPTY to FULL and vice versa.
Last Edit: 1 year, 9 months ago by YLG80.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 9 months ago #2803

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This is the restoration result:

IMG_9203f.jpg


Now I know why there are paint can fuel gauges models with one or two needle pegs.
When I've placed the bezel back in the housing, I've pinched the needle between the housing and the cover in the FULL position.
I had to slightly pull the bezel ring out to release the needle.
It cannot happen when there are two pegs.

Re: Jeep-MB-GPW: 6V SW400507 paint can fuel gauge resurrection 1 year, 8 months ago #2809

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Other info: coil inductance and resistance

fuel_gauge-schematic.jpg
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Last Edit: 1 year, 8 months ago by YLG80.
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