Fuel Gauge Reads Full 1959 Ford 641

Simpleman7140 · Sep 17, 2018

I have a 1959 Ford 641 Workmaster. The fuel gauge stopped working. I replaced the sending unit and 2 new gauges. No matter how I hook them up they read full or empty. It seems when the gauge is grounded to the tractor it reads full. It has 3 terminals on the back. Ground, B, T.

B Battery?

T Tank?

The tractor is original 6 volt with a negative ground configuration.

Is this the correct ground configuration for a 1959 Ford 641 workmaster?

Does ground configuration make a difference in fuel gauge used?

The sending unit reads 15 to 123 ohms out of the tank and 73 ohms in the tank which should be around 1/2 a tank.

Any help would be great.

JMOR · Sep 17, 2018

" It seems when the gauge is grounded to the tractor it reads full." That would cause me to question whether I had identified the terminals correctly.

Steve@Advance · Sep 17, 2018

Sounds like it is wired correctly. Typically grounding the sending unit wire will send the gauge to full, removing the ground will send it to empty.

Try removing the sending unit, wiring it to the gauge, grounding the sending unit housing, put it through the motion and watch the gauge.

If it still won't work, and the gauge responds to grounding/ungrounding the T terminal, then there is a compatibility problem between the gauge and sending unit. With aftermarket parts anything is possible, failure new out of the box is normal.

I would send them back, try another brand/source. Good luck!

JMS/.MN · Sep 17, 2018

Check if the wire is good. It may be cracked and grounding itself.

47fivewindow · Sep 17, 2018

My old truck had a faulty ground to the tank, took me a few tries to figure that out.

stevob671 · Sep 17, 2018

If it is original 6volt gas tractor, it would have been positive ground. 12v were negative ground for diesels.

Simpleman7140 · Sep 17, 2018

(quoted from post at 13:10:02 09/17/18) If it is original 6volt gas tractor, it would have been positive ground. 12v were negative ground for diesels.

Thank you. It should be good on that part. It is gas 6 volt.

Simpleman7140 · Sep 17, 2018

(quoted from post at 09:37:37 09/17/18) Check if the wire is good. It may be cracked and grounding itself.

Thank you.
Side panel is off the tractor and I can get to everything pretty well.
Gauge is out of the tractor. Wire is not touching anything. It ohms out the same as directly to the terminal on the sending unit.

Simpleman7140 · Sep 17, 2018

(quoted from post at 11:58:25 09/17/18) My old truck had a faulty ground to the tank, took me a few tries to figure that out.

Thank you.
I will check that.

Simpleman7140 · Sep 17, 2018

(quoted from post at 09:13:47 09/17/18) Sounds like it is wired correctly. Typically grounding the sending unit wire will send the gauge to full, removing the ground will send it to empty.

Try removing the sending unit, wiring it to the gauge, grounding the sending unit housing, put it through the motion and watch the gauge.

If it still won't work, and the gauge responds to grounding/ungrounding the T terminal, then there is a compatibility problem between the gauge and sending unit. With aftermarket parts anything is possible, failure new out of the box is normal.

I would send them back, try another brand/source. Good luck!

Thank you.
I will do the checks everyone has described. I am thinking bad new parts.

Simpleman7140 · Sep 18, 2018

(quoted from post at 13:10:02 09/17/18) If it is original 6volt gas tractor, it would have been positive ground. 12v were negative ground for diesels.

I misread you post. My tractor is wired as a negative ground. The positive cable goes to the solenoid and the negative cable goes to metal on the tractor.

Is this wrong non original configuration?

Not sure how the original gauge worked for a little while. I have read you can reverse the polarity on the tractor but it can cause issues. Not sure what to do now to get the gauge working.

JMOR · Sep 18, 2018

(quoted from post at 17:28:17 09/18/18)

(quoted from post at 13:10:02 09/17/18) If it is original 6volt gas tractor, it would have been positive ground. 12v were negative ground for diesels.

Click to expand...

I misread you post. My tractor is wired as a negative ground. The positive cable goes to the solenoid and the negative cable goes to metal on the tractor.

Is this wrong non original configuration?

Not sure how the original gauge worked for a little while. I have read you can reverse the polarity on the tractor but it can cause issues. Not sure what to do now to get the gauge working.

f I were you, I would not open another can of worms by trying to switch ground polarity. I and others can do it without incident, but many will ruin regulators in trying. "If it aint broke, don't fix it until you achieve broken." I doubt that your fuel gauge is polarity sensitive. I would get the gauge & sender out on a wood bench and do do some testing.

Simpleman7140 · Sep 18, 2018

[/quote]

I have tested on a bench. The old gauge had 2 terminals. Battery and Tank. I assume it grounded thru the mount. The aftermarket gauges have 3 terminals Battery, Tank, Ground.
The sending unit ohms out thru the wire to the negative on the battery 74 ohms the same as directly to the sending terminal and sending mounting plate. I believe the sending unit is good.

JMOR · Sep 18, 2018

(quoted from post at 18:34:32 09/18/18)

f I were you, I would not open another can of worms by trying to switch ground polarity. I and others can do it without incident, but many will ruin regulators in trying. "If it aint broke, don't fix it until you achieve broken." I doubt that your fuel gauge is polarity sensitive. I would get the gauge & sender out on a wood bench and do do some testing.[/quote]n all gauges heads that I have had experience with (tractors or vehicles), the instrument will read full or empty when 'tank' terminal is either left open or connected to battery (un-grounded terminal).

Simpleman7140 · Sep 18, 2018

[/quote]

JMOR
Went back to the bench.
1. New 6volt battery.
2. Two new gauges I have been wrestling with.
3. New sending unit.

Both gauges will work if hooked up this way.
1. Sending unit sitting on the positive post.
2. Sending unit wire "T" Tank on the negative post.
4. Ground wire on the positive post.

Any other configuration results in full or empty reading.
Does this achieve broke? :?

I have a pic but not sure where to upload it.

Simpleman7140 · Sep 18, 2018

[b:01473b8d3e]Correction to wiring in last post.
this is working configuration.
[/b:01473b8d3e]

JMOR
Went back to the bench.
1. New 6volt battery.
2. Two new gauges I have been wrestling with.
3. New sending unit.

Both gauges will work if hooked up this way.
[b:01473b8d3e]1. Sending unit sitting on the positive post.
2. Ground wire on the positive post.
3. "B" Battery terminal wire on the negative post[/b:01473b8d3e]

Any other configuration results in full or empty reading.
Does this achieve broke? :?

I have a pic but not sure where to upload it.[/quo

Simpleman7140 · Sep 19, 2018

It looks like the only way to get the fuel gauge to work is to go back to the positive ground configuration.
Any information on making the system a positive ground like it came from the factory would be appreciated.

JMOR · Sep 22, 2018

(quoted from post at 15:04:07 09/19/18)

It looks like the only way to get the fuel gauge to work is to go back to the positive ground configuration.
Any information on making the system a positive ground like it came from the factory would be appreciated.

nless told otherwise, I'll assume that this configuration was tried and did not work?
1. Sending unit sitting on the negative post.
2. Ground wire on the negative post.
3. "B" Battery terminal wire on the positive post.

Reverse battery connections such that positive battery terminal will now be attached to tractor chassis,
This is the "B"-circuit generator, so follow the polarization routine on the right, before starting engine. Note that Field wire is disconnected from VR when polarizing. (sometimes the same can be accomplished easier by disconnecting wire from generator Field terminal and using a jumper wire from un-grounded battery terminal directly to generator Field terminal. Small spark and remove jumper wire, reconnect Field wire & start up, now Positive ground.

For reference:

Simpleman7140 · Sep 22, 2018

I wanted to thank everyone for their help. I put the new battery in as a positive ground. Then removed the battery and field wire off the voltage regulator. Touched them together for a little spark. It started right up and fuel gauge works now. As far as I can tell it is charging correctly. I had around 6v with the tractor not running. When running and idled up it was around 7v.
And no smoking wires.

Thank you everyone.

JMOR · Sep 22, 2018

(quoted from post at 19:13:08 09/22/18) I wanted to thank everyone for their help. I put the new battery in as a positive ground. Then removed the battery and field wire off the voltage regulator. Touched them together for a little spark. It started right up and fuel gauge works now. As far as I can tell it is charging correctly. I had around 6v with the tractor not running. When running and idled up it was around 7v.
And no smoking wires.

Thank you everyone.

am happy for you & you are very welcome for any help that I may have been.

Fuel Gauge Reads Full 1959 Ford 641

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