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PostPosted: November 4, 2017, 4:44 pm 
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Location: Scottsdale, AZ
Ever since I bought my 65, the gas gauge has never worked. It just parks between quarter and half full no matter what. I have continuity on the orange wire to the tank. My voltage from the regulator behind the dash outputs between 0 and 9 volts randomly with 12 going in. So I think that is working. The next step was to test the gauge and I needed five volts. Didn't feel like going to buy a bunch of D batteries so why not USB? It worked perfect.

I found an old USB cable and cut off the old end. Pealed off the shielding and stripped the wires. It was an old one, so it just had a black and red wire. And I'm not joking when I say you have about 4 strands to work with.

https://1drv.ms/i/s!Au7oGslkRZsUiqogwC8QVB8F7DWrPQ

Plugged it in and it tested 5 volts even. Hooked up the negative to the bottom post (orange wire post) and positive to the other.

https://1drv.ms/i/s!Au7oGslkRZsUiqoh_73N9JPs7lNgFQ
https://1drv.ms/i/s!Au7oGslkRZsUiqoiXl3eK6NMvc5VmQ

So at 5 volts the gauge should be full. And it was. So glad it is working.

https://1drv.ms/i/s!Au7oGslkRZsUiqof1RbMtvgeeBgZrA

Seemed like an easy way to get 5 volts. If I did it again, I would find a longer thicker USB cable. Thought others would find it a useful way to test as well.

If anyone else has any suggestions on getting my gauge to read, I am open to them. Can it be the float in the tank? Can I test that?

Thanks.

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PostPosted: November 4, 2017, 6:15 pm 
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your gauge moves freely & seems ok...
but it constantly reads 1/4 - 1/2
I would think the sender is stuck or broken & not moving

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PostPosted: November 4, 2017, 6:34 pm 
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Useful plan for 5v instrument service! The 5v gauge output, as you obviously know at this point, simply works in combination with the sender rheostat, to provide a variable ground for the gauge.
Thus, you could easily test the gauge, regulator, and wire circuit with a simple test lamp probing the wire connector at the sender terminal. Since the regulator provides a pulsing 5v output, the test lamp will also pulse as the gauge moves toward full.
Easy way to test the sender is with a multimeter. It should read around 75/90 ohms at empty and 10 ohms in full position when sender is removed and well grounded. if it has the original style brass float, also check that the float is not full of gasoline, a common occurence.

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PostPosted: November 4, 2017, 7:40 pm 
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Yupper! Brass float full of gas!

But the sender is faulty also. I was getting way higher ohm numbers and when I tested it outside the tank with the connections, the gauge went full when pulled up, but would only drop to its usual position when completely extended down. Between 1/4 And 1/2.. So looks like too much resistance. Parts store called. Be here tomorrow.

Thanks Toyz

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PostPosted: November 4, 2017, 8:16 pm 
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The fuel tank sending unit can be taken apart to get to the resistor and metal tang.

Some cleaning with steel wool on the resistor wire and and the metal tang, along with slightly bending the tang fixed my gauge.

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PostPosted: November 4, 2017, 9:02 pm 
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And slick4x4... you were spot on in both accounts. It was stuck with the full float and the sender was bad. But of course I thought the rats nest behind my cluster was to blame. Apparently the gauge was telling me everything I needed to know... lol...

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PostPosted: November 5, 2017, 8:07 am 
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One other tip on gas gauges, make sure you have a good ground on the tank.


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