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

While driving a 1946 Packard Clipper Limousine I noticed that the needle in the gas gauge moved around alot - a considerable, distracting flutter. Is this correct behavior for this car?

The wiring diagram shows a simple circuit. According to a recent post in this forum, the Tank Unit (sender) is a resistive model in which it changes resistance depending on level of fuel.

Is it normal for the float in the tank to move around a lot and cause the needle in the gas gauge dash unit to move a lot as a result?

The 46-7 uses a S-W magnetic type gauge which is fairly sensitive and does make rapid changes but is generally stable. I suspect either there is a poor or loose wire connection, poor ground to the tank or gauge unit, or more likely the sender has developed a condition where the wiper is not making a tight and stable connection to the resistance wire. Oxidation and corrosion on the ground paths to and in the sender or on the wiper or resistance wire is a known issue with senders. The phenolic support the resistance wire is wound around can also become warped or sometimes slightly deformed enough that the wire is not kept in tight contact with the wiper. Any of those issues will cause the gauge to flutter.

The Stewart-Warner sender used on the Clippers should have a resistance of 100 ohms empty and 0 ohms full. It is a project to remove the sender to test but as that is the usual cause of issues it may be the best option. You can see what the resistance is doing with an ohmmeter. When moving the float from empty to full and back the meter should have a smooth consistent resistance change throughout the full range (If the meter automatically changes ranges during the test it might jump a bit at the scale changes). If the meter jumps around or does not register a smooth change in resistance that slight difference in a magnetic gauge will be picked up and the fast action of the movement will cause the gauge to flutter or read erratically.

Here is quick rundown of the fuel gauge system and a basic test that can be done without removing the sender.

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I've heard, but never tried, that a drop of glycerine on the gage needle pivot will damp flutter.

If you attach a ground wire to the top post on the gauge, it should show full and be steady. One way to check the gauge. Also you could hook a resistor (in series) between zero ohms and 100 to also check the gauge, this would show if the gauge is steady or not, the readings wouldn't really matter. Maybe a 50 ohm resistor would display a half tank, not sure. You would just be looking for movement and that the needle is steady.
With this checkout you can tell the gauge is good and then drop the tank to look at the sender, which is most likely the problem in my opinion.
Wes

Quote:
Wesley, I couldn't agree more - the sending unit is the PRIME culprit, most of the time. I am in the process of having KM Lifestyles Mfg. make me a new sender for my '39 Six as I write this and will hopefully get back to reliable tankage level reporting. I hate not KNOWING what is 'in the tank'! Chris.