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EricD

Starter Generator question

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RedbarnRick
I have to agree with renegade the regulator has been the culprit any time a charging problem has poopped up, I would also suspect brushes if you are only getting a small amount of output voltage.

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Bunky
My S/g always just quit charging, one time it was the bushing went bad in the end, it would start but wouldn't charge... ( the armature was shorting on the fields) and another timne the Regulator went bad....

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Dadsy98
I saved this for reference. This is from member Al Eden: ... ground the F terminal to check the generator, but you should use a voltmeter on the A terminal,or watch the ammeter for a charge. If the generator has shorted turns in the armature, it may still load the engine down and not put out. Also if the cutout terminals in the regulator aren,t closing and connecting the A terminal to the battery you won't see amy current on the ameter and the armature will sataurate and load the engine, measure the voltage at the A term and it may be 18v or more. if not connecting to the battery properly. If you ground the field [F term.] and it charges you have a bad requlator. The generator has 2 field coils and is a composite. One field is a series coil, super heavy wire, and in series with the armature. This provides the start circuit. The generator side is a shunt field connected to the armature on one end and the F terminal one the other end. The Voltage regulator puts a ground on the F terminal. This causes the generator to charge, When the generator rises to about 12.2 volts the cutout contacts make and connect the battery to the A terminal of the gen. When the voltage reaches about 14 to 14.3 volts or the current 10 amps, the F terminal contacts break and open the field circuit. There is a resistor across the contacts so the field is still energized with a small current and the generator output drops, the contacts in the reg close and energize the field again and the generator output goes up again and the cycle repeats. The output is controlled by the vibrating contacts. they make and break up to 300 times a second. Because of the reluctance of the armature and the inductance of the fields, the output of the generator looks constant. If you look at the output with an oscilloscope you will see a DC level with a high frequency AC ripple on top of it. You can actually see the output change as the generator is switched on and off. The control coils in the regulator control the output with one or 2 coils. If you have the long regulator used with the long frame generators there is one coil with many turns of fine wire that is connected in the regulator to the A terminal of the Reg. This is the voltage control and it pulls against the contact that switches the field to ground. Less than 14 volts at A terminal the spring holds the contacts together turning the generator on. The 14v setting is controlled by adjusting the spring tension while operating the system on a fisture. The next coil is the current control. This coil has about 20 turns of very heavy wire [about #8] this coil is connected from the A terminal of the regulator to the one of the contacts of the 3rd set [cutout set.] the contacts of this set [current reg set] are connected in series with the voltage contacts to ground, so that opening these contacts also breaks the field circuit to ground. A spring pulls these contacts closed also, and the spring is adjusted so that when the current exceeds 10 amps the contacts break and they function just like the voltage control section. Vibrating to limit the current. The 2 section regulator [used with short frame generators] works the same way except the series current winding is wound around the outside of the voltage coil and the magnetic pull from either winding controls the same contacts so both voltage and current regulation is accomplished with one set of contacts. The last set of contacts is the Cut out contacts. This set switches the A terminal of the Gen to the battery. When the generator output excedes 12v the contacts close and connect the A armature out through the current windiing in the regulator to the battery terminal of the regulator to the battery [through the ammeter if one is used.] When the voltage drops to 11.9 the contacts open to keep the battery from feeding into the armature and cooking it. [disconnecting the battery] The most common failure other than brushes and bearings which affect both starter and generator functions is the generator field coil being burned out. This only affects the charging process, and is caused by the the regulator NOT regulating and running the generator at full output all the time. If your field coils are burned out, replace the regulator or have the regulator recalibrated or the new field will go in a short time if it is ran for very long periods. The starter side will still work perfectly.

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