Packard Forum Index » Pre-War (1899-1942)

I have a 1940 110 coupe that has a 12 volt negative ground battery. My question is has the starter been changed or does it matter the car starts and drives. I thought the starter would run backwards if battery was negative ground. But it seems to work ok. What else do I have to do to convert to negative ground? The only electrical hook up now is starter and ignition I am going to put a 12 volt alternator in it.

Have yout tried a search, 12-volt conversion has probably been covered here 100 or more times.

Your starter is not polarity sensitive. Your ammeter is and you'll have to reverse the terminals if you want it to read properly. Solid state components are polarity sensitive and will need to be replaced, if you have any.

I'm curious why you're converting, unless you intend to add AC there really isn't much worthwhile to be gained by the conversion.

It is already partially converted when I bought the car and I would like to use a concealed modern radio and it starts great.

It is already partially converted when I bought the car and I would like to use a concealed modern radio and it starts great.

I believe the 40 temp gauge is mechanical so not an issue but if the oil gauge is electrical it and the fuel gauge probably need a reducer. A Runtz device would be better than a straight resistor as it provides a more stable output voltage but downside is each gauge needs one of those. Heater motor needs a resistor and for the best coil efficiency, you want the terminal connected to the distributor to be the same as the ground. In other words, if you have 12v negative ground you want the negative terminal of the coil connecting to the distributor. If the coil was changed to a modern type 12v coil it is easy to do but if it is the old style coil with the armored cable it is difficult and the increased efficiency may not gain that much when running 12v for the amount of effort. There should also be an added ballast resistor in the wire feeding voltage to the coil if you are running 12v. Modern coils can either have the resistor built in or else an external resistor needs to be added in order to protect the life of the points.

A suggestion would be that you might think about having the starter itself converted to 12v. The 6v motors do turn fast so engines start quickly on 12v but there have been some who have done the conversions and kept the starter motors stock and then came back on the forum to report their starter motor had been damaged when the nose casting cracked or was completely broken off. Consensus is the increased torque and speed of the starter running on 12v causes the pinion to slam into the end of the casting with such force that the casting eventually gives up.

G'day tvrpman,
to PackardInfo, I invite you to include your '40 110 Coupe in the Packard Owner's Registry.

My 1940 coupe may or may not be original, but seems like the windshield wipers are electric, you may want to add them to the list of items to check.

Electric wipers would be correct original equipment for your car.

Correct and apologies. I forgot all about the electric wipers on the 110 and 120s and a resistor would be needed.

I also forgot another item. If the car has Overdrive that is a bigger issue. A resistor will not work properly on an OD because how much of a voltage drop a resistor provides depends on the size and amount of current flowing thru it. Overdrives require varying amounts of current depending on the state they are in and with a resistor depending on current flow, it would need to be sized for worst case -- around 20 amps max when the solenoid is pulling in. At low current need times there would be a real possibility of not enough voltage drop and burning out a relay or part of the solenoid. Unlike the R11 ODs, no 12v repro parts are available for R9s and those electrical parts are hard to come by and expensive.

If you do need something for an OD, there used to be an ebay seller providing a 12v to 6v 20 amp electronic converter for use with ODs. His listing has expired and I didn't find another so I have no idea if he still sells them. Electronic converters used with ODs must be rated for use with motors and coils which eliminates a lot of the lower current conversion items typically found on ebay for use with radios etc but you might check and see if you can find the OD unit.

After reading all this correct info on what you'll need to do to accomplish what you want to do (use modern 12V neg Grnd devices and ensure easy starting), I think it might might be easier to get a 6 to 12 volt converter, attach it to your battery and nest it next to the battery, run the wires from it to an installed modern device, and you're done.

I ran the wires to a modern cigar lighter receptacle which replaced the original one so I can push a charger in there and plug it into my iPhone, wireless earbuds, etc. that need 12V-neg grnd. When I'm not using it, I just put in the original cigar lighter (whose contacts don't match up with the modern cigar lighter receptacle, so it doesn't light).

I added a toggle switch next to the battery box so I can shut off the converter when I don't need it so it doesn't draw any juice.

As far as easy starting.... I bought a better grade compact charger at Harbor Freight with a read-out that also turns from red to green. It has a set of clip connectors and a set of ring connectors for permanent use. I attached the permanent connectors to the battery, brought the wires up from the battery box next to the toggle switch and then left the charger under the front seat cushion.

If the car is going to sit for a week, I just ease up the rear part of the seat cushion, grab the plug for the charger and plug it into an extension cord. If your 6V battery is always fully charged, you'll have no trouble starting, unless it's for a different reason than battery.

By accident I ended up with 2 Optima (gel) batteries, so wired them in parallel for maximum cranking power, but one would work as well.

Attach file:

---

  (845.61 KB)


  (314.89 KB)