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

Is it possible to test the dash gauge by grounding the wire from the tank unit? My dash gauge moves about 1/8 inch regardless of quantity in tank. Thanks Dell

I don't know of any way to accurately test the 48-50 gauge units without having another good sender although grounding the wire and have it do very little is suspicious.

The gauges work with a pair of heaters in series influencing each other. When the heater in the sender gets current it heats a bimetal strip which closes a contact to ground. The ground lets the heater in the gauge move the needle and when it cuts off lets the gauge heater cool. When it is heating, it's bimetal strip raises the needle. Not exactly sure how the heaters interact but suspect the heaters may be wound using a special wire that changes resistance when it changes temperature. The changing resistance on one controls current being able to flow and affects the heating on the other.

Here is a bit from an old Motors Manual. The fuel gauge works the same way except instead of pressure bending a diaphragm, the float works a cam affair and its position is what biases the bimetal strip. The oscilloscope photo is what is happening electrically as the sender heater opens and closes the contact going to ground.

Do not believe there are any reproductions and NOS Packard senders are rather scarce. IIRC, BDeB posted a few months back that some Ford senders of that era will drop right in and may still be found at some of their vendors. Maybe a search will find that post as I don't remember if he gave any years or models.

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Thanks HH; I have tried three tank units and dash gauge reacts the same. I was afraid of grounding the sender with out help. One of the tank senders is an extra for my custom which I sold, if any one needs one let me know. I guess it time to wiggle under the dash. Dell

Yes Dell; I could really use that tank sender for my 49 Super Eight. Let me know how you want to go forward.

Dave O

Dave O; Please PM me your personal contact information and I will contact you when I get my problem solved. Dell

Dell, you might check out Mar 1, 1948 SC Vol 22 #3. If you do the test they mention with one of your senders only using the oil or temp gauge, if one of those gauges does as they say but the fuel gauge does not then that would be proof the gauge is bad.

Don't forget there were two senders used in those years -- one for the small and another for the large tank. I once had a NOS sender and there was a 17 stamped in black ink on top of the mounting flange. No idea if the 20 gal sender had a similar stamp.

The length of the arm is probably the difference but I cannot say for sure and don't have measurements. I neglected to measure the small sender when I had it. If we had a number the arm could probably be lengthened or shortened as needed if a Ford sender was tried or if you find a Packard version that was for the other tank

Thanks Howard; That will at least eliminate the wire from sending unit to dash gauge. When the upholstery was done one wire was drilled into and separated, could be more damage behind headliner. Dell

The sending unit should have the Packard part number stamped on the underside of the mounting flange. I know that one removed from a Custom 8 had the number stamped

Has anyone tried the plastic float used on Jeeps?

Help! pulled most of my hair out with this fuel sending unit. Gauge works fine when out of the tank, put it in and no go. Anyone have an idea. Have tried two different sending units, ground is grounded. Dell

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