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I appreciate it, though I'm not sure it would be needed. Since what I have in mind would be that someone can buy a generic sender with a linear response, and have that adapt as well as reasonable to the factory gauges.

The other thing is that, as far as I am aware, the usual rheostat senders have a low resistance when full and high when low. But David's chart is the opposite.

Edit: Actually seems like low ohm empty and high ohm full is the standard, at least for GM.

Thanks dp. I don't know, but would assume, that the gauges are electrically identical.

Howard or dp do we know for certain that all 3 senders used the same signaling scheme?

Thanks. It's surprisingly non-linear, but maybe that's how the gauges read to begin with.

Since you have 0.2A at 20 sender ohms, then with a 5V regulator that implies the gauge has a 10 ohm resistance. This checks out with the 50 and 100 ohm values also. So we see that about 22mA is required for the gauge to read 0; and open circuit is required for the gauge to read 100. I can easily make something that will convert linear-linear. Following the exponential decay curve could be difficult, but might not really be necessary as you can just calibrate the gauges to what looks good. For example, where normal coolant temp and oil pressure read right in the middle, and where the gas gauge reads perfect near empty. Will have to think more on a design that could replicate this curve well.

David please confirm, the "gauge percentage" of 0 is like your empty tank, no oil pressure, and cold engine; and "gauge percentage" 100 is full tank, high oil, and high temp?

P.S. Howard, I think that's what I'm getting at. I can make something where a 10-70 ohm sender will pretend to be a 20-120 ohm or whatever. Of course, if the range only needs shifted then a simple inline resistor would do the trick. But for these, even though a 10 ohm would make a 10-70 sender read correct when low, it would never read about more than about 85% high.

Good idea but I don't have a 48-50 car to try anything. So I'm not sure what to do with that info. Someone else would have to try it 😃

As many of you know, the 48-50 cars used unique senders (gas tank, temp, etc.) that are pretty much no longer available.

I can make a module that can electrically "convert" between any generic aftermarket sender that physically fits, and the corresponding gauge. It would only require a brief calibration.

But to do this, I would either need someone to send me a spare gauge, or be able to send some pictures plus maybe do a couple basic electrical tests on a gauge. (Not sender.)

Please let me know if you would be interested in this project. The pricing would be very competitive in comparison to alternatives.

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Certainly. And not often found on sites dedicated to other makes or models.

I actually complimented it on my second post ever here 😃

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=24406&post_id=235489#forumpost235489

Idk, parts book gives them all the same.

https://packardinfo.com/xoops/html/modules/partslist/viewgroup.php?partslist=1955-1956&groupnumber=4.1337&PlateNumber=31&cat=23#resultanchor

I gave it a shot and it looks like there's 2 tabs on each side so 4 total. No idea how you could remove one of these non-destructively.

Bad picture but hope this helps.

I have an extra I can send you if you want. Should polish up well.

It could be done but the high beam wire would be awkward to connect to anything since it's a socket and not a screw termination. Would need to run a wire from the foot switch in place of the normal wire.