Rare 1965 VDO Instument/Gauge, who knows more??

[Carparc]

I just found this VDO Instrument and have never seen one like this before, very rare combination of Amps and Oil.
Who has seen one before or knows in which cars these were used?
The date on the back clearly says May 1966 (sorry for typo in the header)
The gauge is NOS, never been used before, came with the original box (no part number though).
In the box I also found installiation instructions, see pictures.

I am very curious to find out more about this, thanks for your input!

Henk.

[Carparc]

Talked to him and also Hollywood Speedo, they knew of converted ones, something they did also by request, but never seen an original one like this.
It might be something that could be specially ordered from VDO, I mean if you look at the instructions it is meant for Porsche...

Henk.

[304065]

Wow, never seen anything like it.

The diagram is interesting, clearly a 356 era 6V diagram, note the battery cells.

Also, it says use 10 square mm diameter wire, that is really about 7 AWG (an odd size), the stamped instruction says use #10, which means 10AWG, which has a smaller diameter (5.26mm^2).

Ammeters and load meters are cool, you can see the position in the circuit, if the load exceeds the power coming from the generator then it's negative, if the generator is greater than the load then it charges the battery and goes positive. Used to be fun to start the airplane engine and watch the loadmeter drop, then watch it go positive as the alternator charged the battery back up from the start.

That said, running hot wires around inside the cabin is both a source of voltage drop and kind of dangerous besides-- I've seen plenty of cars with badly chafed wiring behind the gauges, not sure I'd want another wire up there carrying a full 50 amps. . .

I don't see an external shunt in the instructions. All the ammeter really is, is a voltmeter that measures the voltage drop across the shunt. The more current flowing through the shunt, the more voltage drop there is, and that voltage drop is measured by the meter and presented as the proportional amperage. Of course there is no way that 50 amps of current could ever flow through the tiny little meter movement, it would light on fire.

Anyway, most ammeters have a shunt somewhere, the modern VDO gauges you buy have it internally, I would be interested to see the inside of this gauge to see where the shunt is.

[davep]

All the ammeter really is, is a voltmeter that measures the voltage drop across the shunt.

Almost, but not quite. The basic meter is an ammeter that responds to the magnetic field generated by the current flowing through the coil. A voltmeter is an ammeter that measures current flowing through a calibrated resistor. You are correct that most ammeters will have a shunt, either internal or external, since most meter movements are sensitive enough that only a few milliamps are required for full scale deflection. The shunt multiplies the current capacity of the meter movement.

Seeing how the instructions are dated 1959, it would be originally designed for a 356 installation. With the the 1966 manufacturing date and 12V rating I'd guess it was made for 9xx series installation. I think 6 AWG wire would be suited for the 50 amp current.

[Carparc]

I couldn't upload more than 4 images earlier, here is the second page of the instructions that came in the box. This page describes the oil pressure part of the gauge.
In the left lower corner I see a date (printed vertically), probably indicating the publication date, it says 7-62 which makes me believe this was more intended for a 356?
The gauge drawn in this instruction however shows a single gauge, intended for mounting under the dash, completely different than the gauge we are discussing.
Thanks for the info so far, very helpful and correct, however has anyone seen this instrument before and if so in what car??

Thanks, Henk.