‘34 electrical issues and 8V->6V conversion
 

Hi all, car novice here, just trying to keep my late grandfather’s ‘34 roadster running! I’m having problems burning up a couple of condensers. Each one lasts maybe 15min, and then the engine sounds like it’s missing before dying completely (I’m using NOS ones found on eBay, no idea on specs; I recently bought some Napa’s IH200 but need to solder a ground strap and figure out how to attach the other end to the brass part of the coil).

Car is running off an 8V battery, positive ground. I’ve measured voltage at the ignition coil (rebuilt coil by Skip) at 3.7V with ignition on (sometimes when I flip the ignition on, I read a full 8.5V! I have a NOS ballast resistor I plan to try later). With the car running the voltage reading jumps around between -30V and +30V (I expected a steady smooth voltage while running due to the action of the condenser, perhaps I’m wrong?). I haven’t checked the output voltage of the generator + voltage regulator yet.

Last question, I’m thinking about converting back to the original 6V positive ground (anyone know which battery would fit in the wire cage under the driver’s floorboard?). Other than simply swapping the batteries, is there anything else I need to do? Do I need to adjust the generator and voltage regulator? Also, will the car have enough juice to start, ~2.6V?

Thanks so much, this sounds like a good community here! -Brian

Re: ‘34 electrical issues and 8V->6V conversion
 

Most nos condensers I have tested were no good due to age.

Re: ‘34 electrical issues and 8V->6V conversion
 

Sounds like several issues here.

1. NOS condensers will most likely not work because of age.
2. The 8v battery is not a good idea, need to switch it back to 6v.
3. You need to know what the generator is outputting.
4. A digital voltmeter will not measure correctly around the generator and plug wires, you need an analog meter.

I would stop trying to run the engine until you figure some of this out, it would be very easy to damage the coil along with the capacitor.

Re: ‘34 electrical issues and 8V->6V conversion
 

If your voltage is varying coming to the coil, i would suggest checking the wires and connections coming from power to switch to coil. The ignition switch may also need a cleaning.

The car wasn't converted to 8v, an 8v battery was installed instead of a 6v. Put a 6v in er and retest with your new analog meter.

Re: ‘34 electrical issues and 8V->6V conversion
 

It won't start with 2.6 volts to the coil. It drops even lower
when the starter is running. A 6 volt Optima battery will
fit in you box. You need a minimum of 3.5 and max of 4.2
8 volt batteries cause to many problems. G.M.

Re: ‘34 electrical issues and 8V->6V conversion
 

To clarify the 3.5-4.2 volt at the coil: that is with engine running. When testing in the garage with engine stopped, you can expect to measure about 3.0, plus or minus a few tenths of a volt. (6 volt battery) Later when engine is running, points open 20% of the time, it will jump up to the 3.5-4.2.

Re: ‘34 electrical issues and 8V->6V conversion
 

That will happen if the engine just happened to stop with the points open. While points are open there is no current, and therefore no voltage drop thru the resistor, so you will see full battery voltage at the coil. When that happens, just bump the starter to get the points closed.

I agree with the others, condenser is the likely suspect. But could be a bad coil, and these coils are known to be fragile. Both will often work fine when cold, but then fail when they warm up.

BTW, when working in the garage don't forget to turn off the ignition switch after each test. With engine stopped, ignition circuit is drawing its maximum current. Is hard on the coil. You want to minimize time switch is on with engine stopped.