Generator Stalls

ken freund

March 25, 2014
Filed under RV Tech Q&A

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I have an Onan MicroQuiet 4000 generator in my 2003 Four Winds . I bought this coach in 2005, and the 4kW generator has worked well until recently. I always make sure the generator crankcase oil level is full before each trip. The generator uses little, if any, crankcase oil.
We took a camping trip four months ago and the generator started fine and ran smoothly until the end of the microwave oven’s cook cycle, when the generator stalled out immediately. This stalling happened every time we cooked something in the microwave. The generator always restarted easily and ran fine after it stalled. I adjusted the needle valve until the generator sounded like it was running a little more smoothly and rapidly, and until today it looked as if I had solved the problem.
The generator normally runs at a pretty high rpm. The generator is a single-cylinder engine that runs on regular-grade gasoline from the motorhome’s 70-gallon fuel tank. I top off the gas tank and add STA-BIL at the end of each trip. Every month I start the generator and run it with the air conditioner on high/cool in order to keep the generator in good condition. Today I started the generator, and ran it with the A/C on high for 30 minutes. When I turned off the A/C, the generator immediately stalled and shut off. Do you have any idea why my generator starts well and runs under load smoothly, then stalls out at the exact time the load is shut off?
Bob Haynes | Valrico, Fla.

This definitely seems like a problem in the genset’s control module, where the change in load isn’t being correctly responded to. It may also be related to a governor adjustment (which requires a frequency meter, voltmeter and 4kW resistive load) that should be done by a qualified technician.
According to Onan, your genset should be a Spec J model, which has flash trouble code capability. This fault should set a flash trouble code that will show up on the control panel. Following a fault shutdown, first-level fault codes should be illuminated; the indicator light will repeatedly blink one, two or three blinks at a time. One blink indicates shutdown due to high temperature. Two blinks indicates shutdown due to a loss of engine oil pressure. Three blinks indicates shutdown due to some other abnormal condition — I suspect yours will do this.
For a one-blink or three-blink first-level fault code, one touch to the stop button brings up a second-level fault code. This secondary type of code consists of one, two, three or four blinks, a brief pause, and then one to nine blinks. The first set of blinks represents the first digit and the second set of blinks, the second digit of the fault code number. A governor actuator fault code is 15. A controller (processor) fault should log a 42 or 43. The fault code stops blinking after five minutes. Press stop three times within five seconds to restore blinking. Note that the last fault logged will blink even after the condition that caused the shutdown has been corrected. Although you can read the trouble codes, it’s best to seek professional help when troubleshooting generators.
 
– Ken Freund


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