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Hi you big resource of knowledge. I'm going to convert my 1949 Packard to 12V and the only problem I can see is the solenoid for the overdrive (B/W R-9). I've been reading that the solenoid has to be changed to a 12V solenoid because it's not possible to put a voltage reducer on it. This is as far as I can understand because it's two coils inside it. My question is: Why can't I put one reducer on each coil? The relay is supposed to be OK with 12V...

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I don't believe you will find any 12v components for an R9.

The R9 solenoid has a different length plunger than a commonly available 12v solenoid for the R11 to that wouldn't work and the wiring is different anyway. If you knew the individual solenoid coil current draw, it might be possible to calculate the proper resistor for each coil but being that one of the relay coils is in series with the solenoid hold coil, it might prove more trouble than it's worth.
As to using the R9 relay on 12v, since it cannot be easily isolated the effort and expense of finding another R9 relay if plans didn't happen to work as advertised makes that an experiment I wouldn't try.

Assume you would also be going to negative ground with the 12v conversion so if I were contemplating a change, since the OD has a one wire feed off the starter solenoid I would remove that wire and power the entire OD with 6v using a voltage reducer module such as this one. That way the entire OD is working at the proper voltage, no resistors to calculate and no need to change anything else.

The fellow making the units has a nice writeup at the end of his listing of some of the other advantages. While he doesn't specifically address positive ground cars, with the individual input leads to the module it should be possible to use it with positive ground but maybe worth an inquiry if you are going to keep that part stock.

An added benefit is if you get the 20 amp version of the module there is capacity available to work a couple of other hard to modify items. The Electromatic clutch (if you have one) comes to mind. Also, if you sell the car and the next owner wants to revert back to 6v, he doesn't have to worry about reversing a lot of changes.

How about running two six-volt batteries in series, running all the original 6-volt components from one battery, and using both batteries for whatever reason you're changing over. You'll need to install an alternator, but that's not a big problem. That's the way our 1940 Zephyr is set up.

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Don't know if this will help but my R11 6 volt solenoid draws an initial 10 amps to start then drops to 2 amps to hold.

Thanks for responding. HH56, I have now ordered the voltage reducer as you suggested. Hopefully that will solve the problem.
West Peterson, I was thinking of doing it that way first but I have read that the batteries will not charge equally.
Again Thanks and I will post the result when it's done.

Hi Jappe,
You can also make your own voltage reducer. I made one for my radio, and have tested the volatge, but do not have my car running yet. The parts cost me about 10 euro, but it was an evening of work to solder it all together. The 60$ isn't a bad price.
my blog

Well, you might be able to make your own faster than mailing one from the US. customs in germany is really slow, don't know if spain is faster. Good luck.
Mike

Interesting electrical problem. I think in the long run Ohm's Law is going to win and it will be back to the drawing board.

It might be better to adapt a mechanical actuator to replace the solenoid. A cable or lever with a detent could be a more reliable way of holding the the engagement over a long drive, maybe less smoke.
Bernie