Suddenly my generator output voltage dropped to around 80 VAC.
The nameplate tag has long since come off but with the help of the service manual the model number could be derived to be 10HDKAG 61731x. It is a 4-pole revolving field, brush-type, reconnectible, 10.0kW, single phase, 1.0 power factor, 60Hz unit. The reconnection is wired with T1-L1, T2-T3-L0, T4-L2. Which provides two legs at 120 volts each.The hour meter indicates 1,398.8 hrs.
Here are the things I've done so far in an attempt to figure out what is wrong.
- The wiring all looks good, tight and clean.
- I took the measurements on both sides of the main breaker mounted on the gen-set.
- The voltage regulator is part number 305-0875-04. I can adjust the regulator down to say 50 VAC per leg but no higher than the 80 VAC or so. I'm thinking the regulator is OK since it does adjust. At this point that is all I have to go by.
- I disconnected the regulator and applied 12 VDC to the field winding. The voltage measurement between L1-L2 was 105 VAC. Just within spec per the service manual. Both L1 & L2 were balanced when referenced to common at 52.5 VAC. When the regulator is connected it drives the field winding to -23 VDC. I don't know how much the field winding should be to get 120 VAC.
- I measured the frequency to be 61.5 Hz. Within spec.
- The power plant is a Kubota V1305-B diesel engine. The throttle was lock wired at the factory and painted over. It is clear that it has never been touched.
This unit is in a 1996 Monaco with the front generator slide out.
As difficult as it will be to climb under the motorhome to get at the back of the generator with the front slide out rod right smack in the middle of the work space I'm thinking of going for a brush set replacement. If possible I would like to replace the bearing since it is so old. I have no idea how the bearing comes off at this point.
Any thoughts about this problem and my plan for the brushes and bearing replacement?
Thanks for your valuable time.