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

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.

Before going this route and maybe reinventing the wheel how about someone trying 40-55 Ford senders reproduced by and sold by Ford vendor Dennis Carpenter. According to Motors Manual the Ford gauges and the King-Seeley gauges Packard used appear to be electrically the same.

BDeB said the Ford senders should work but the question before saying so would be are they all available and if they are a direct replacement would be by trying one to verify they work and to see if they fit the Packard openings or if an adapter of some sort would be needed. Another question would be if the fuel sender float arm length or bend would need to be modified.

I did not spend any time looking for what oil and fuel senders are on the Carpenter site but one of our posters with a 22 or 23 series was going to try their temp sender and report back so hopefully that will happen before too long. If oil and fuel seners are not available then they might be a candidate for your project.

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 😃

HPH

Here’s the data I recorded on my ’48. The test set-up featured a rheostat/potentiometer in lieu of the cylinder head sensor. What I didn’t record, but would likely be a second order effect, was the ambient air temperature. I think I also had a battery charger hooked up just in case the voltage regulator output was dependent on the input voltage.

dp

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One thing I've been curious about with the 22 - 23 series gauges is if the built in cooling off period offered by the pulsing contact is needed. If a straight always on resistance sender is used with those earlier gauges will the lack of any gauge bimetal cooling off period cause the needle to slowly creep up after being on for a long driving period. The later King-Seeley gauges used in 51-6 had the straight 73-10 ohm resistance senders and later gauges had a similar build configuration that was always on. I believe it has been proved the later senders will not read properly with earlier gauges but if the correct straught resistance value could be found for the earlier gauges, was the heater resistance value or type heater wire and bimetal used in the gauge also different in those later years to accommodate the always on senders.

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.

HPH

The data applies to the temperature gauge only. I was trying to get more than 3 calibration points, so I estimated a 10-point scheme. Zero is COLD, 100 is HOT.

The nonlinear characteristic may be the age of the test article alone. I could be a bit of roughness in the 'normal operating' positions.

Howard

I believe the gauge will function OK with steady state current levels, albeit lower than the peak value in the pulse width modulated scheme. I'm trying to hold the bimetal at a particular temperature, and I can get there with a steady heat input, or on/off cycles of, when on, excessive heat input . . . much like heating a home in the mild weather.

IIRC doesn’t the service data indicate that a fuel sending unit may be used to trouble-shoot either the fuel level or coolant temperature instruments? If my memory hasn’t turned to mush it would then be a question of resistor values and calibration. I’ll sign-up for if I ever have my fuel tank removed I will repeat the ‘fixed resistor’ test on that instrument.

dp

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?

I have a NOS sender available for test. 403066 if memory serves...

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HPH, I would think they are identical or at least be so close as to have any differences be insignificant. This service article has the mechanic use a fuel sender to test the oil and temp gauges so the signals from the other senders must be the same pulsing that I documented with the fuel sender.

As additional info, farther in that same service counselor the dimension differences between the 17 gallon and 20 gallon fuel senders is given. If a Ford sender is available from Dennis Carpenter it might be possible to verify or duplicate a needed Packard tank distance.