Diesel generator intermittently producing 117V and 104V at irregular intervals

Before I haul my generator off to a repair facility I thought I'd see if anyone can give me a clue what might be going on.  It's a Marathon pancake head driven by an Isuzu 3LB1 engine producing a nominal 10 kW.  For awhile the generator will produce  117-120V then for awhile it produces ~104V, changing back and forth at irregular intervals (not a high speed fluctuation; minutes to an hour or more).  The change does not seem to be related to heat or load and it does not seem to produce intermediate voltages.  The Outback inverter charger produces about 4.6 kW when fed the higher voltage and 4.2 kW at the lower voltage, which seems to make sense.  The genset has about 1,000 hours on it.  I'd very much appreciate any thoughts on this.

Comments

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    How is the voltage regulated on that unit?  Mechanical or electronic or ?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • john.sundogjohn.sundog Registered Users Posts: 5
    Electronic regulation.  I should also have mentioned the frequency remains stable at a hair over 60 Hz.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Well I know that on my 3000w gasoline screamer the Frequency is steadier than the voltage, I can adjust it a bit on the carb settings, but yours is diesel... can you adjust the idle/running speed at all to see if it changes the V output any?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • john.sundogjohn.sundog Registered Users Posts: 5
    My apologies for the delay, westbranch and Johann - it seems I've had a technical problem interacting with the forum due to inexperience.

    1. Westbranch, thanks for thinking about this issue.  The step voltage changes don't seem to be associated with a change in engine RPMs, though I'm not certain about that.  The changes seem to occur at arbitrary times, not triggered by load or environmental conditions as far as I can tell, so I haven't been able to monitor an actual change, just the before- and after-conditions.

    2. Johann, the link you provided has given me a path forward.  Many thanks for your efforts.
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