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

The horns will work fine on 12v, you'll just need to take the cover off and adjust them slightly to the proper tone.

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Simple enough. Coupled with the new starter and instrument voltage regulator, there's no need for any 6V circuits on the car. Excellent.

You existing instrument voltage regulator will work just fine. It takes 6v-15v input and outputs 5v for the gauges.

I used my original one on my car, and everything works just fine. If you look at the part numbers you'll also see the 51-54 instrument regulator is the same as the instrument 55/56 regulator. Ford used the same one into 70s.


You can use a 6v harness on a 12v conversion, but not a 12v harness on a 6v conversion. 6v, half the voltage, but usually twice the amperage. Hence why the wiring on a 6v car is thicker generally than on a 12v car.

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We must have different parts manuals. The way mine reads is 54-56 used the same regulator and 51-3 used another. The 54 ambulance used the 51-3 version which is interesting but IIRC, that may be because I think I read the ambulance dash carried over from the 53s. Question is what is the difference in regulators they would decide to change -- capacity, voltage, mounting or ??

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I knew the 54 was the same at the 55/56, so I assumed the 51-53 would also be the same.

Maybe it was superseded or something. Can't think of what would be different between the two. But, showing the 54 (6v) and the 55/56 (12v) use that same one, at least gets the point across that those 'Chopper" style Voltage Regulars are not too picky about the input voltage above 6v.

Also, the '54 Supper Clippers used the '53 dash cluster, not the '54 Special/Deluxe "sweeping" cluster. So I would assume either they used the '53 IVR, or they worked just fine on the 54-56 IVR.

Agreed the 54-6 regulators are not particular and am not saying the 51-3 won't work on 12v too. I just don't know what is different but do find it interesting Packard made the change for whatever reason while running what is essentially the same gauges. Hopefully someone who has done a conversion will chime in with solid info that the 51-3 regulators will work on 12v without issue.

Better yet would be if someone knows if there is a significant difference between the regulators. I am thinking it may be capacity for a third gauge. IIRC, one of the books said the grand plan was to have the 55 changes done in time for 54 cars but something wasn't ready and things got pushed back. If that were the case and they had the ordering done for a 54 introduction it might be as simple as being able to run the third gauge on senior cars.

Thanks for the tips, Kev. The car shows signs of wiring modifications for purposes I haven't figured out yet, so I don't know exactly how it deviates from the factory wiring diagrams. Coupled with a new system voltage and aged cotton insulation I don't trust, I'm planning to replace every single conductor on the car with modern TXL wire, a central relay and fuse center, textile loom, and welding cable for the high-amperage connections. All documented for easy diagnosis.

It sounds like the instruments will be good with the factory regulator, but I'll bench-test its output on a 14.4V feed to be sure. If it doesn't kick out 5V, I'll go with a modernized IC or a Ford regulator.

If it doesn't kick out 5V, I'll go with a modernized IC or a Ford regulator.

It is a pulsing output between 0v and 12v (or 6v) with a frequency on duration to give an average level of a 5v output. On most meters the pulsing will be hard to read as 5v with an ordinary meter. Here is the output as viewed with a scope and what the regulator looks like. The heater bends the bimetal strip to work the contacts. How fast it opens and closes the contacts depends on load and voltage in.

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I am constantly amazed at how different these old beasts are from the fuel injection and transistor-based circuits I'm used to. Now I'm wondering if the gauges would run on a "real" 5VDC instead of the pulse width modulated system voltage. No real need for the information, since they'll clearly work on the pulsed voltage. Just curious. Might test it, but I'm reluctant to risk rare components.