Generator testing

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The car is a 1932 V12, the generator has only one lead that connects to a voltage regulator. The regulator has two terminals one that connects back to the amp meter and the other that runs back to the startix which is where the lead coming out of the generator is attached. What is the method for testing the generator and or the regulator as my amp gauge is showing a discharge while the engine is running. The wiring is correct according to the Pierce wring diagram for this year. Any assistance would be appreciated.

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Is it a Delco three brush generator? What are you running for a cutout? There are several different styles, don’t assume the cutout is correct. Some photos would help. Be sure your battery is charged before you begin to test it. Ed

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Also let us know if your battery is 6 or 8 volts. The charging system will not charge until the regulator calls for a charge. If you use an 8 volt battery, you need to adjust the cutout, or more appropriately, the cut IN voltage on the regulator.

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I would not run an 8 volt battery. There is no reason to run one. The car will start and run fine on six, that was fine in the era, and it’s still fine today with a properly sorted car.

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the cutout or regulator is a Delco two post. The generator is a 3 brush internal grounded so only one lead is coming out of the generator. I believe the generator is also a Delco, can’t see a tag as it is installed in the car and not visible. the wiring diagram for the car shows the lead coming off the generator connecting to the cutout and another lead running to the startix. On the other side of the cutout the lead runs to the amp-meter. This is a a 6 volt system with a positive ground.

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Bill, three brush Generators are standard in all Pierces of this vintage. NO Pierces use a voltage regulator. Thus they DO NOT require any polarizing of generator or cutout. Your volt reading at the cutout wire going to the amp gauge will read battery voltage with the car off. When the engine is running the voltage will increase and the amp meter should charge. remove the cap on the cutoff and see if the cutout pulls the contacts down asking for a charge to the battery. By moving the third brush you will increase or decrease the charge rate of the generator. any off idle use should pull the cutout in and keep it in. the only other other time you will see it “cutout” will be if the battery voltage is higher than the set rate of the generator. check this stuff, if you still have neg amps, remove the cover over the brushes, see if you see small arching at all brushes. No, then check for dirt build up or stuck brushes. nothing found, pull the generator for rebuild. Karl

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V12 generators are often swapped out over the years, and there are several years where Delco or Owens were both fitted. Also, cut outs and cut out regulators are also installed as replacements, thus with no photos or tag numbers to refer to, and often many cars having the startix removed or disconnected from the car, its nice to know what one is actually talking about. So, my question stands, what is the generator and what is the cut out being run. About 20 percent of the cars I see today have modern electrical upgrades under the old equipment covers. If his 32 V-12 is all stock, then proper diagnostic procedures can proceeded. I don’t have a 32 wiring diagram here at the house, and I cant remember if the 32 eight and twelve run the same cut out. The 32 generator may also have the internal resistance winding that cuts down the charging rate with temperature. Can someone post the National Service info on the system, and the diagram? Ed

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The generator does not have a tag, there is a number stamped on the case 9344. Here is a picture of the cutout. The generator is not producing any current. It is out of the car and went to a rebuild shop.

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Bill,

If you go to the Library section and put in your year and model there is a on line Owners Manual for the 12’s and there is a parts book you can get, if that helps.

Bill

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The 32 twelve uses a Delco 265B cut out, with a temperature shunt in the face plate that cuts the charging rate by 50% at operating temperature. Carge rate cold is 22 amps, shunted down to 12 at full temperature. If you dont have the shunt in the generator, as many go missing or are removed, you can then run a 33 to 38 cutout/regular combo. If you cant get the shunt to work correctly, set it up for a much lower charging rate otherwise the thing will melt the armature. Generator for 32 is a 927L. Looks like you have a correct cut out that is probable a replacment and will require adjustment for running open between zero and -2.5 volts discharge. Good luck! Ed

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I sent the generator out for rebuilding but it was found to have an internal short which was fixed. I installed the generator and it is still discharging however the amp meter needle is jumping between 0 and 10. Is this because the cutout is not functioning correctly? How do you adjust the cutout as mentioned above. Also, someone mentioned that the third brush should be adjusted. How is that done? I don’t see any external adjustment screw or bolt.

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Hi Bill. The ‘third brush’ adjustment is done by moving the brush itself and it’s holder. Look closely at the top brush visible with the band removed from the generator. The brush holder has a locator in a slot. The entire brush and holder can be slid on this slot to move the brush ahead or back. This movement is accomplished with a screwdriver used as a prybar.

VERY GENTLY place a screwdriver against the opening in the generator case, place the other end on the brush holder on the pin that goes through the slot. Then GENTLY pry the holder either fore or aft to change the output of the generator.

Hope this helps.

Greg Long

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Bill,

I got this off the web.

“Looking from the brushplate side, slide the third brush in the direction of rotation to increase, opposite to decrease”

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Thank you for the responses and I was able to adjust the brush.

[Author]

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