Kubota RTV400Ci


The Kubota shop manual came in and here's the trouble shooting.

When I arrived at the farm the Kubota had trouble starting it was progressively getting worse.  The battery was 5 years old and it lives out side in the elements.  I jumped started the RTV brought it down out of the field and replace the battery. A few days later it failed to start again.   I placed a DVM on the battery and it was low and obviously not starting.

The engine did not have an alternator further review of the engine it  appeared to be a one cylinders air cooled engine with 2 wires coming out in the center near the starter.  It appears to have a stator for power generation.  I received the Work Shop Manual (WSM) and it only cost 91.00 bucks. 

  1. Check all fuses.

Stator checkout

  1. The WSM states stator Charge Coil Resistance should be approximately 0.3 ohms. At the left rear I raised the tailgate disconnected the 2 wire connector and took a relative resistance measurement and the resistance was 0.1 ohms.  I also measured the resistance from each of the contacts to chassis ground the measurement was open. I used my FLUKE DM 88 Automotive Multimeter.
  2. With the stator disconnected I configured the Digital Voltage Meter (DVM) to measure the AC voltage coming from the stator and started the engine.  The voltage measure was 32.50 - 32.95 VAC.  Note: The WSM does not specify a voltage.  The voltage being at 32 volts is a good thing it appears the the stator is good and the rectifying of the AC component would put it in the right range for the rectifier. 32/2 VAC translates to around 16VDC.
  3. After turning off the engine I connected the stator back up and tried to find the voltage regulator which was the hardest part of the job.


  1. The regulator was discover behind the drive back in between the tailgate behind the intake plenum.  You need to remove the 3 bolts to get at it.
  2. The WSM states that the regulating voltage factory specifications is 14 to 15 Volts.  With the engine running using the FLUKE DM 88 Automotive Multimeter measuring set to measure VDC from B+ to chassis ground I had no voltage.  Regulator has no output.
  3. I checked the stator's input using the FLUKE DM 88 Automotive Multimeter measuring set to measure VAC and it also read 0 volts with the engine running. Regulator input is shorted.
  4. With the engine powered off and the ignition off I disconnected the regulator see the photos.  I measure pin L to ground and found 4.8 ohms which is the battery light to the console.
  5. With the regulator disconnected I started vehicle and took stator measurement again which was 32.95VAC and I checked the IG connection ignition which was 12.05VDC the battery voltage.  My conclusion is that the regulator failed this was most likely due to a bad battery over time that caused the failure.  The good news is the stator appears good which means the flywheel and or engine does not need to come off.  One of the photos show measurements I took on the yellow sticky's. The part is being ordered

  If this has been helpful let me know alabama_dave@hotmail.com