Re exciting a 6 v Genny ??

Husker44A

Well-known Member
Friend of mine has a 51 GMC pickup and the genny isnt working. No power output. Cant remember how the restart it. Any help ? Thanks guys.
 
Polarising or flashing the dynamo . This is how I re energise 12 volt dynamos on Ferguson tractors , I suppose it will work the same on a 6 volt .
Two terminals on dynamo , small is field large is main . Engine off dynamo [ generator] terminals off . Attach battery to the polarity configuration you want , ie. either positive or negative to earth . Take a wire from the battery terminal that is [u:b499ed33a2]not[/u:b499ed33a2]connected to earth , brush this against the field terminal [ small one ] once or twice for a second only , reconnect terminals to generator / dynamo and check output and polarity .

You can also ' motor' the generator , this will polarise it and show any defects in the internal wiring . [u:b499ed33a2]This is for positive to ground wiring .[/u:b499ed33a2] Disconnect the dynamo , join the field and main together with a wire to 12 volt neg . connect positive to the frame of the dynamo . If all is well the generator will turn sedately , if it skips or stalls there may be a crook bearing or bad winding .
 
Are you asking about polarizing the regulator?

With the engine off, use a jumper wire, spark the "A" terminal of the generator to the non-grounded battery terminal. Only touch it, just enough to get a spark, don't leave it connected!
 
The generator on your truck should be an "A" circuit. You need to make momentary contact between BAT and ARM terminals on the regulator or battery hot and the "A" post on the generator HTH Mike
 
You polarize a Class A genny system (NOT the Voltage Regulator) by using a small jumper wire to momentarily flash jump from BAT on the VR over to its GEN/ARM terminal and you should get a small spark. Same things accomplished by jumping from BAT (or any hot ungrounded battery voltage source) to the gennys ARM post.

For a procedure to determine the cause of no charge on Class A systems work through my Troubleshooting Procedure linked below. It includes instructions to full field a genny by grounding its FLD post to see if non charging is the fault of the Genny or the VR or other causes.

John T
John Ts Troubleshooting
 

A generator will produce a charge even if it has not been "polarized".

If the generator is NOT producing, it probably needs new brushes.
 
Actually, if there is absolutely no residual magnetic field whatsoever left in the soft iron field poles it wont produce sufficient energy to pass any initial current through the field windings which is needed to create higher magnetic field strength. A genny works by rotating the armature inside a magnetic field, but if theres absolutely no magnetic field she never starts the generation process which then causes current to flow through the field windings which greatly increases the field strength. Of course, it doesn't take much residual magnetism to start the process and a gennys fields would have to be magnetically depleted big time to prevent it from charging especially if she turns fast enough.

The harm comes if the genny is polarized opposite form the battery polarity which can damage the voltage regulator.

Hope this helps, fun chattin

John T
 

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