The short sweep electric fuel gauge manufactured by Auto Meter for the Ford 73-10ohm range is calibrated for the original Ford factory supplied, non-linear, fuel level sender design. If you view the gauge dial itself, you will notice that the halfway point in the gauge is in fact not centered in the field in order for the calibration to match this special sender.
The Ford Fuel Level sensor with a 73-10ohm range operates with the following ohm ranges for Full, Half, Empty, and Below Empty:
Full: 10ohms
Half Tank: 25ohms
Empty: 50ohms
Pointer Width Below E: 73ohms
If you have replaced the original equipment Ford sending unit in your vehicle with an aftermarket sending unit, you may notice that the gauge will match the sending unit at the Full and Empty portions of the scale, but that the readings in between will not match up. The reason for this is that some aftermarket senders operating with the 73-10ohm range now utilize a linear movement instead of the original non-linear scale. The comparative ohm reading difference for Full, Half, and Empty have been supplied below for your reference.
Full: 10ohms
Half Tank: 41ohms
Empty: 73ohms
As you can see these numbers differ radically from those of the factory Ford sending units, and have a drastic effect upon the gauge readings.
In the event that you have this situation, we recommend one of four options:
OPTION 1 You can attempt to seek an original equipment fuel level sending unit directly from Ford for your vehicle.
OPTION 2 If you have an Auto Meter short sweep electric gauge, you may send it into us for service and we can modify the gauge to work with the after market linear sender. The cost is $25.00 + return shipping, as long as there is nothing else wrong with the gauge. (prices subject to change without notice)
OPTION 3 You may use the Auto Meter Full Sweep Programmable fuel level gauge and opt to use the Custom Calibration section of the gauge instructions. The Programmable version is not available in all series, but can be designed and built through the Auto Meter Custom Shop in nearly any standard incandescent lit series (meaning no through-the-dial LED lit designs in Custom Shop). See the following link for Custom Shop http://www.ampcustomshop.com or contact us directly at 866-248-3657 for alternate options:
OPTION 4 You may purchase one of our 240-33ohm scaled gauges and the matching #3262 sending unit. If this sending unit will not fit your specific tank type, you will likely have to retain your existing sender to serve as a fuel pick up source, and then create a new hole on a flat surface on the top of your tank for mounting the new sender. We recommend the 240-33ohm units because they are a broad and fairly linear scale, and provide a very accurate reading of the fuel level in the tank.