The love of my life stopped generating full power on one 120 leg a few weeks ago so I took the cover off and found a bad bearing. I am not sure the bearing is the source of the low power but it is a good place to start. I finally got around to taking it apart today.
Haven't had that much fun in at least 10 years. Don't miss it, either. (Did enjoy ripping things apart and getting them back together and run. But getting up and down off the floor is just too dern difficult these days.)
Oh, My God!! Reseating brushes on the sliprings... Not to mention ringing out the Field windings to find out if they are open... Best of luck and I hope the fix is an easy and inexpensive one.
If it still Started using the Genend as the Starter, then all the Field Windings are still good, and that is not the issue... I would look at the Stator windings, and compare resistance of both legs... Should be within a few mil-ohms of each other...Since I am not in Alaska, for this winter, I can not offer any Parts, but next spring that will change... If you have a good MotorShop local to you, you might ask for a Rewind Quote for the Stator Windings...
Brgs won't usually knock out one leg nor will field windings. If it isn't a bad outlet or breaker, usually a stator problem with 1 leg of the winding. Lose one leg, usually simple or fatal in most gensets. Takes a pretty good one before the cost of replacing a rotor or stator is worth it. Wish it wasn't so, but it is Most gensets use one voltage reg and field to handle both legs.
These Onans are regulated by the Field to Stator Winding Ratio, and not by any AVR Circuit.. They have a DC Motor Winding on the same Rotor as the rotating Field Winding... This is an ALL OLD SCHOOL Design...
I will fix it if possible, I can't find anything similar that is produced today. Diesel, 3KW, 1800 RPM.
Just got a quote on rewinding a 7,5 kw.....$1300! They said they would have to send it to Atlanta because it was oval. So we're going to retrofit a Chinese 10kw ST head onto the engine.
Nice meter... Guess it isn't the field windings. 2K Ohm scale, reading within 1 Ohm difference, if my math is right.
Might also check from the rings to the shaft...seen weirder things. But keeping fingers crossed for a brush issue. Lots cheaper to fix.
Can it be the fields have de-energized. I know we had some CAT SR4's that needed a 12v source to excite the fields and once 120/240 was sensed the relay would remove the 12volt source? Just curious if this can be the same issue.
No not really, as the same windings are used as the Starter Motor, when cranking the Genset, and that Flashes the Fields, every time you Start the engine...
I think I found the problem. This collector ring has one ring with a flat spot. That brush would have to be on its game 100% of the time to remain in contact with it.
I have to think that any good starter rebuilding shop can sort that out for you if can get the rotor out and take it to the shop. I'd hate to try to fix that one without turning it.
