I reread the article and I see what your saying since the spring is apart of the circuit, shimming it with a nonconductive material would have them scratching their heads as to why all of a sudden the horn stopped working. Plus it must had been some pretty bumpy roads, reminds me of our old gravel roads. Sometimes the blade wasn't set right and it would hop causing a bunch little ridges in the road and with any speed it would give you a good shaking.
Oh the good old days!
Wes

For such a simple switch and so much goes into it.
I used your colors and made a color version. It makes it much easier to see how it works. "A" is where it touches to complete the circuit, also while doing this I just notice a quick check to see if the Horn Assy. is working. Just ground the blue screws at the back of the steering wheel. Easy test and you wouldn't have to take the steeling wheel apart. Touch the screw no horn sound, then the problem is from there back. But if the horn does sound then the problem is in the switch assy.
Wes

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Howard, I found a cross section drawing to add to our collection of drawings. This is from Vol. 17 No. 13, July 1, 1943.
Wes

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Just a little more information on the heat control. From Vol. 17 no. 09, 1 May 1943 Service Letter.
Wes

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This is what happened to my sending unit after Costco switched to Ethanol. I don't know how many months but I think less then a year. Car wasn't being driven at the time. I did find the brass float laying on the bottom of the tank, what was left of it, just a skeleton.
Wes

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Well had a little set back. Made another one of these for my 20 gallon tank and slowly added five gallons at a time and never got a good enough reading while filling it up. After putting 20 gallons in the gauge read under 3/4 full and also my needle kept bouncing around.
Tried grounding the sender wire at the tank, also couldn't get a full reading and needle kept jumping. This made me think that maybe the gauge is bad, but knowing this is a six volt system and I hadn't checked my battery. So I found the battery low (Forgot how low but under 6 volts.)
Put it on the charger and left it for the night to think about it.
Next day battery fully charged (Optima 6 volt red top battery) checked by grounding the gauge top post and meter showed full scale and no jumping. Next went back to the tank grounded the wire to the sender and checked gauge and it shows full, no jumping. Remove the Ground and needle goes back to a little over 3/4 and no jumping.
Remove wires and ohm out the sender and find it's reading about 15 ohms.
Next step after I drive it around and burn off some gas I'll pull it out and see what happen to my sender and why it's reading about 15 ohms.
Wes

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

Here's something from "1945 Service Counselors". The only thing I have heard is if it is stuck closed, it may result in over heating of the carb.
Wes

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Well, with the sticking Clutch Pedal fixed. I took it out for a spin. Next project why so much play in the Steering Wheel. I'll probably watch Mark Lamberts video on him adjusting his steering on his 39 Packard to give me some ideas as to what to look for.
So it looks like I'm moving ahead, I also noticed a few more items to look at but first the steering.
Wes

You might want to checkout:https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=19912&forum=10&post_id=196244#forumpost196244
More information here:https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=21586&forum=2&post_id=211889#forumpost211889
Wes