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Voltage will vary with the condition of the battery, the draw on it and the generator output. Expect variation between as low as 6 and as high as 8 but more typically between 6.2 and 7.4.

PS. Hard to believe those ancient NE condensers can still be reliable, I'd suggest burnishing the points and replacing with AL869.

As Dave said, the coil should be seeing exactly what the battery is seeing and allowing for wire runs and some possible loss at switches or connections, maybe a tenth less. With the engine off coil would be supplied with the standing battery voltage of 6.3v and with engine running it would see what the generator is providing. On later cars with a voltage regulator this would be adjusted to provide a maximum of around 7.0-7.4 volts.

From what I remember about third brush generators (not very much) with only a cutout relay, they have no voltage regulation and voltage output is kept in check by the battery and connections to it. With the battery keeping the voltage in check, the brush adjustment mostly changes current output and is adjusted for the output to be in the range of 18-20 amps (per the 10th and 11th series specs) which will be enough going to the battery that it will be kept charged when head lights are on.

If you are seeing 10-11 volts I would really wonder about the battery or the condition of some of the connections and would also think any light bulbs in the car would be very vulnerable. There are a few stories on the forum from people who had accidentally disconnected the batteries while the car was running and lights were on. Sad result was their expensive head light bulbs blew because of the sudden voltage surge out of the generator when it lost whatever regulation the battery was providing.

HH56, the generator control supplied as OEM for 1934 3-brush generator does have an early form of voltage control in addition to the cutout. Original factory literature on it has been posted on here several times years back and I could repost if needed. The generator control is an Owen-Dyneto 21262. The NAPA/Echlin replacement (nla) was VR 755 and functioned similarly.

Good to know but if that is the case then it would seem that in order for a voltage to be able to climb that high the voltage regulator is seriously misadjusted or maybe not functioning. If it works anything like the later regulators maybe there is a short in the field wire or perhaps the contacts in the voltage regulator have stuck.

Here's a couple of pages.

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  Dyneto charge regulator ad 1.jpg (31.78 KB)


  Dyneto charge regulator 1.jpg (346.56 KB)


  Dyneto charge regulator 2.JPG (266.78 KB)

Thanks for the info and while the regulator works a bit differently from the later models, if the voltage is actually 10-11 volts the same items might be worth checking.

Just like the later regulators, there is a resistor that is placed in and out of the circuit to regulate current to the field to control the voltage. If there is a misadjustment or field wire is shorted or if the contacts are stuck closed the resistor will not be able to be placed in the circuit. In effect just like grounding the field wire to test operation on later units, the generator will be unregulated.

I see the field fuse but have no idea how sensitive the fuse might be as far as blowing if the field is shorted or as a means to prevent high output. If it is as reliable as the main TL fuse on the 55-6 models, some of us know how that works. In many cases damage is done before the fuse even thinks about blowing so maybe the field fuse is the same as far as protecting output.

Yes HH56, I fully agree that if the system voltage is much above about 7.4, there is a fault with the generator itself or the control unit. What I don't have a feel for is what effect that might have on the function and longevity of the repro NE coils. The fault with my NE repro coil was mechanical, not electrical.

If they are getting a constant 10-11 volts they would most likely overheat. If that is the case something inside could be expanding and acting up or maybe the insulation is reaching a point where temperature is causing it to break down.

I would expect the early coils and probably the repros which are most likely made using modern coils as a starting point would prefer the same 6-8v that the current 6v coils prefer and that is what they should get with the direct feed. Modern 12v coils also prefer a lower voltage to keep from overheating or having a lot of current flow thru the points. They require some kind of internal or external ballast resistor or a special resistance feed wire to provide them a steady voltage of around 8-9v.

I would suggest measuring the coil supply voltage very carefully when at rest and when the engine is running and maybe also measure one or two other places not directly connected to the coil. Reason for another measuring point is to find out if voltage is actually out of spec thruout the system or if when the coil's magnetic field collapses, back emf from the coils is also being read by the meter and skewing the measurement.

Turns out my multimeter I was checking the voltage output of my generator with was screwed up. It’s putting out around 7.5vdc. Thank you all very much for trying to help me out with this, one more quick question, what do you like to run your spark plug gap at? I see Packard in the service letters recommends .025. Could too large of a spark plug gap say .035, cause the coils to heat and breakdown?

I have been using Autolite 306 plugs gapped to 0.025" for many years, total satisfaction. I never saw a reason to try a plug gap different from the factory spec.