Packard Forum Index » Post-War (1946-54)

Hi, Does anyone have any tips for working on a fuel sender unit for this year? I'm working on cleaning out the gas tank and I pulled the sender unit,and it looks to be in great shape overall. I am getting a resistance reading on my meter but it bounces around quite a bit when I move the float up and down. I don't know what the correct resistance range is for a working unit and I'm not sure how I should proceed, so any info would be a big help. Thanks!!

48-50 senders are not straight resistance units so it is hard to measure with an ohmmeter. It has a heater which opens and closes a bimetal strip. The rate of the opening and closing is controlled or changed by the amount of pressure the float produces on the strip as it changes with fuel level. The length and frequency of the on time works another heater and bimetal strip in the gauge to move the needle.

Here is a couple of illustrations from an old Motors Manual with the general idea of how it works.

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One way you can test your sender would be to use a couple of jumper wires. One to ground and the other to the gauge wire. Turn the key on and move the float up and down. See if the gauge works and tracks smoothly or if there are any dead spots. If the sender looks to be in decent shape then it should work since there is no resistance unit to corrode or warp. If there seems to be problems then that type sender should go to a company which has the tools and knowhow to work on them. AFAIK, NOS are all but gone. Rebuilt exchange units are available but expensive.

One poster on the PAC forum had a seriously rusted and non rebuildable unit so did some experimenting. He found a universal 0 ohm full and 30 ohm empty sender would work electrically but to mount the universal sender needed an adapter and then a bit of rework on the adapter to fit the tank.

Wolf can rebuild them-advertises in Hemmings