Fuel Tank Sending Unit Fix

[Theorangetiger]

My fuel gauge wasn't working at all and I isolated the problem to a broken wire inside the sending unit. Originally the wire was crimped or mechanically stamped into place on both ends.
I was able to solder one end to the wiping arm of the sender. The other end goes to ground which is any part of the sender housing. I drilled a hole for a 1-72 machine screw in the side of the housing and trapped the loose end of the wire under a nut & washer. I used very fine solder wick and turned a coil in it so it should be able to handle the movement, which is actually very slow as the float rises and drops with the fuel level.
Replacements are available but I suspect the broken wire and/or corrosion on the face of the resistor would be the most likely failures inside the sender and are a cheap fix.

 

[Agent 861]

Nice fix -Mine doesn't show full on on the gauge maxing out at about 9 gallons even when the full to the brim . Is the sender calibratable ? -Karl

 

[Theorangetiger]

I don't think you can calibrate them but it's probably worth removing it and have a look inside. Removing the driver side trunk spring makes this reasonably easy. You can measure resistance in different positions and they should be 228 ohms in the empty position, 68 at mid and 22 at full.
I'd check and clean the surface of the resistor and make sure the blade is moving correctly. In my photos, the first shows empty and the second shows full. I'd see what is going on in that position.

 

[KettleCarver]

Where do you place the test leads to obtain a reading?

I am going through this right now with my sending unit. When hooked up to the harness, it does not move the gauge in any position.

 

[Theorangetiger]

Without removing the sender you can test for continuity and/or resistance between the terminal on the sender and ground. If you get nothing, I would suspect a broken wire in the sender.

 

[KettleCarver]

I have it out of the car now. Neither of the wires appear to be broken.

So, to test, just put one lead on the plug-in and the other to ground?

 

[Theorangetiger]

Correct. Any part of the housing is ground. It doesn't look like there's any significant corrosion on the face of the resistor. If this checks out you should check current on the wire going to it. It should be 10V because it comes from the instrument voltage stabilizer.

I found a lot of information here: https://www.google.ca/url?sa=t&rct=...20gauges.pdf&usg=AOvVaw3x4ghNCJEaBMVIGnnwW1AS

 

[Austin Healer]

Nice fix -Mine doesn't show full on on the gauge maxing out at about 9 gallons even when the full to the brim . Is the sender calibratable ? -Karl

calibration is usually a matter of slightly bending the rod to the float... you can test the unit out of the car by attaching a ground lead to the top of the sender. manually move the float through the range of movement. if the gauge goes to full with the float at the top of its range it's probably hitting the inside of the tank when installed. If it doesn;t read full when moved manually, the fault is in either the sender or the gauge.

 

[KettleCarver]

Correct. Any part of the housing is ground. It doesn't look like there's any significant corrosion on the face of the resistor. If this checks out you should check current on the wire going to it. It should be 10V because it comes from the instrument voltage stabilizer.

I found a lot of information here: https://www.google.ca/url?sa=t&rct=...20gauges.pdf&usg=AOvVaw3x4ghNCJEaBMVIGnnwW1AS

Thanks, that is really good information!

 

[Theorangetiger]

It really is all you need to know about the water and fuel gauges. Probably the most unexpected thing I learned from it is the fact that other than the faces, the inner workings of the two gauges are identical. They are interchangable.