Off topic generator help needed

Check for "residual" voltage on the output. Should be some AC voltage output from the stator windings before any output breaker etc. Usually anything over a few volts will build up if everything else is good. 0 or just a few volts you need to flash the field to boost it up. Many Onan manuals will have the procedure. Basically match polarity at connections to the exciter field leads and apply DC there. A 6 volt dry cell is plenty or I have used the smallest voltage I can get out of the generator starting batteries THROUGH a probe type test light so the lamp limits current flowing. In an emergency you can just scratch a wire on the terminals with the generator turning at full governed rpm and get it to go.

I am guessing you lost the residual from the vibrations resulting from the bad bearing or might have swapped the exciter field leads when reinstalling it and simply need to flash it.

If you have good residual or flashing doesn't cause voltage to build up AND STAY UP, then the other checks you mentioned need to be done. The exciter field or rotor or the main field on the rotor may be shorted from the parts scrubbing. disconnect the field from the rectifier heat sinks and test. If those are ok, the rectifier diodes will be arranged in two groups of 3 all same polarity and are usually stud mount type so you can easily replace them. To test each one you can remove the stud end from the heat sink. I replaced all three when I found any one bad. They are available from suppliers like DIGIKEY and MOUSER, sometimes eBay etc. Mainly match up the stud size and polarity and most any amperage and voltage will work and be better than what was originally installed. I think I wound up with 40 amp and 400 volt on an 85KR I fixed once.

OH......before you do all this, check the exciter breaker on the control panel isn't tripped. That would be can easy fix, but it may have tripped for a reason. If you need more troubleshooting, I can supply ONAN literature or its probably available online if you search for ONAN 900-0150 Service manual The wingspan site pdf file is what you want.

Did the exciter rotor rub the exciter field poles??? If so you will need to make friends with a motor rewind shop....WA7OPY

Check for "residual" voltage on the output. Should be some AC voltage output from the stator windings before any output breaker etc. Usually anything over a few volts will build up if everything else is good. 0 or just a few volts you need to flash the field to boost it up. Many Onan manuals will have the procedure. Basically match polarity at connections to the exciter field leads and apply DC there. A 6 volt dry cell is plenty or I have used the smallest voltage I can get out of the generator starting batteries THROUGH a probe type test light so the lamp limits current flowing. In an emergency you can just scratch a wire on the terminals with the generator turning at full governed rpm and get it to go.

I am guessing you lost the residual from the vibrations resulting from the bad bearing or might have swapped the exciter field leads when reinstalling it and simply need to flash it.

If you have good residual or flashing doesn't cause voltage to build up AND STAY UP, then the other checks you mentioned need to be done. The exciter field or rotor or the main field on the rotor may be shorted from the parts scrubbing. disconnect the field from the rectifier heat sinks and test. If those are ok, the rectifier diodes will be arranged in two groups of 3 all same polarity and are usually stud mount type so you can easily replace them. To test each one you can remove the stud end from the heat sink. I replaced all three when I found any one bad. They are available from suppliers like DIGIKEY and MOUSER, sometimes eBay etc. Mainly match up the stud size and polarity and most any amperage and voltage will work and be better than what was originally installed. I think I wound up with 40 amp and 400 volt on an 85KR I fixed once.

OH......before you do all this, check the exciter breaker on the control panel isn't tripped. That would be can easy fix, but it may have tripped for a reason. If you need more troubleshooting, I can supply ONAN literature or its probably available online if you search for ONAN 900-0150 Service manual The wingspan site pdf file is what you want.

[quote="ccjersey"]Check for "residual" voltage on the output. Should be some AC voltage output from the stator windings before any output breaker etc. Usually anything over a few volts will build up if everything else is good. 0 or just a few volts you need to flash the field to boost it up. Many Onan manuals will have the procedure. Basically match polarity at connections to the exciter field leads and apply DC there. A 6 volt dry cell is plenty or I have used the smallest voltage I can get out of the generator starting batteries THROUGH a probe type test light so the lamp limits current flowing. In an emergency you can just scratch a wire on the terminals with the generator turning at full governed rpm and get it to go.

I am guessing you lost the residual from the vibrations resulting from the bad bearing or might have swapped the exciter field leads when reinstalling it and simply need to flash it.

If you have good residual or flashing doesn't cause voltage to build up AND STAY UP, then the other checks you mentioned need to be done. The exciter field or rotor or the main field on the rotor may be shorted from the parts scrubbing. disconnect the field from the rectifier heat sinks and test. If those are ok, the rectifier diodes will be arranged in two groups of 3 all same polarity and are usually stud mount type so you can easily replace them. To test each one you can remove the stud end from the heat sink. I replaced all three when I found any one bad. They are available from suppliers like DIGIKEY and MOUSER, sometimes eBay etc. Mainly match up the stud size and polarity and most any amperage and voltage will work and be better than what was originally installed. I think I wound up with 40 amp and 400 volt on an 85KR I fixed once.

OH......before you do all this, check the exciter breaker on the control panel isn't tripped. That would be can easy fix, but it may have tripped for a reason. If you need more troubleshooting, I can supply ONAN literature or its probably available online if you search for ONAN 900-0150 Service manual[/quote]

Thanks for your suggestions. The leads on the field were so long inside the cabinet that I didn't have to disconnect them. I did flip the exciter breaker a few times. Main thing is it was powering a big well pump before they quit with it. It been sitting at my shop for 2 or 3 months because I only have time to work on what is needed today. Got tired of looking at it fri afternoon & had a peek & a poke. I will try everyone's suggestions & see what happens. Thanks everyone!!!

Was it making power before you fix it,or was the loss of power why you check it out? With the cage gone on the bearing, the rotor would have been push hard into the field poles. It will make a lot of heat in a very short time, and ground the winding out. Find f1 and f2 and excite it with 6 to 12 volts DC keep track of the + and -. The ac should jump up above 60 volt all the way to 150 maybe higher. If the exciter is grounded you can kiss the vr good bye.If you know how disconnect f1 and f2 and meg the winding....WA7OPY