Gas gauge reading wrong

[chuck35truck]

I used the FFR gas tank and all components. I have the gauge cluster and the supplied Ron Francis wiring kit. I connected the plug to the sending unit and the wire plug to the appropriate plug on the gauge cluster. All the other gauges work properly.

When I fill the tank to almost overflowing, it reads 3/8 empty. When it is almost empty, the gauge reads full.

Any suggestion on where to look to fix this problem?

[Papa]

What is it calibrated for? What gauges do you have? FFR sending unit should be 16-158 Ohms.

[j33ptj]

So the gauge is controlled by a potmeter that connects to the float, when the float is up (full) the resistance is different from when the float is low. The resistance in the circuit controls the read out on the gauge, so it sounds like you have something put together the wrong way around. Or that the gauge is not matching the sending unit.

[edwardb]

As mentioned, the sending unit Factory Five supplies with the kit is the Ford range 16-158 Ohms. I always check them before installation. Easy to do with a VOM across the pins. You can confirm they're functional and in the proper range. Short of the sender itself being defective, the important question is what gauges you have. Speedhut gauges are configurable so it's a matter of following the instructions for the proper calibration. Autometer gauges, on the other hand, are preset. If that's what you have, the box should be marked with the range provided. I received the Autometer gauges with my truck kit and the box indicated the proper Ford range. They can't be hooked up backwards. It's a resistance reading. No polarity.

[Pat Landymore]

Do you have your dash lights/headlights connected? If so, turn them on and see if the indication on the gauge changes.

I had something like that early in my ‘35 build (using standard harness and the individual gauges supplied with the kit). Discovered my gauge, (not the dash lights) wasn’t properly grounded. Ran a separate ground wire for the gauge itself and all was right with my gas reading.

[chuck35truck]

I will pull the sending unit and and check the output. I have the speedhut gauges. Thank you for the tips

[Papa]

I will pull the sending unit and and check the output. I have the speedhut gauges. Thank you for the tips

With the speedhut gauges, you want to connect the cable with the button on it to the gauge. Power the gauge. Press and hold the button to enter calibration mode, then release and press the button repeatedly until the needle is at 7/8th full mark to set the gauge to the Ford 16-158 Ohm setting, then press and hold for 2 seconds to set it.

https://thefactoryfiveforum.com/attachment.php?attachmentid=110985&d=1563722437


https://www.youtube.com/watch?v=16-i8zBLqgA

I'd do this before pulling the sender.

[chuck35truck]

Thank you. I will try this first.

[ranitablam]

Hey man, it's been resolved or not? I am living in Rockville (https://yourdetail.com/rockville-md.php) and looking for the same solution.

[chuck35truck]

Yes it has. The gauge needed to calibrated. It did take 2 persons as the ohm meter was reading higher than their standard setting for ford sending units. I had a friend move the float from empty to full and now it works great.

Thank you for your assistance