Replaced Sending Unit, Fuel Gauge not reading correctly.
On a warm day (almost 100F outside, prolly warmer in the cab), my fuel gauge gave up. Figured the original sending unit went bad and ordered a new one. New one showed up, and correcly read 40-140 ohms as desired. I removed the old one and found it to be scaled with some rust and figured that was the issue. Installed new sending unit, the fuel gauge is still acting zany. I read my shop manual for my 52 Ford F-6 and it looks like I may be able to replace a fuel gauge with out replacing the cluster, but it also has a method for bench testing the gauge. Unfortunately, the book doesn't tell you how to remove the gauge!
If your "new" sending unit is an aftermarket type offered by one of the parts vendors it will not work correctly. EVER. They are just not the right type of sender, not compatible with the stock gauge. I also bought one and it is useless. For the stock gauge you must use a stock sender. If you change out your fuel gauge that sender may work.
There was a long discussion about this issue over on the Fordbarn forum......unfortunately I found out AFTER buying it and trying to make it work. I found an original sender (put on a new float) and my gauge works perfectly.
Just to clear things up, this is what I think I understand now:
The King-Sealy (Ford Stock) principle sending units supply a full 6V through the heater wire in the gauge in the form of a square wave with the duration of the "on" being the variable determining the gauge reading. The longer the duration, the more fuel in the tank. It is this full 6v of current which heats the bi-metallic strip in the stock gauge that causes the gauge to read via a small gear train (that may adjustable?). Most after market sending units are simply a variable resistor which sends a constant voltage to the gauge, lessening that voltage as the fuel level goes down. Therefore, the sending units signal doesn't heat the bimetallic strip in the gauge as much. Unfortunately, the calibration of the after-market sending units and the stock gauges don't match up very well due to the differences in the principle of the signal.
Well, I don't know what is bad... I replaced the sending unit because I thought that was it... but it is an aftermarket and so it is incompatible with the gauge. I can ground out the gauge and it goes (beyond) full. I would be interested in a stock sending unit,so if you have one and are willing to part with it, PM me to make arrangements.
1955: Ford replaced the original 6V fuel sending sending unit with: B5AF-9275-A.. Fuel Sending Unit KIT / This unit does not include the float and float rod.
You have to use the original parts from the old sender because this sender was used in: 1948/55 'conventional cab' trucks, 1949/51 Ford Passenger Cars & 1952/55 Ford Station Wagons & (car based) Sedan Delivery's.
This is not the same sending unit used on other 1952/55 Ford Passenger Cars.
WESLEY OBSOLETE PARTS in Liberty KY has 1 = 606-787-5293.
GREEN SALES CO. in Cincinnati OH has 1 = 800-543-4959.
1C-9280-A (replaced 1C-9280) .. Dash Fuel Gauge / 1951/52 all trucks / 1953/55 P Series Parcel Delivery
For a NOS gauge, try Early Ford Store in San Dimas CA (earlyfordstore.com).