I just completed a 2200 mile round trip from Fort Worth to Bristol, TN over the last week.
My Onan Marquis 5000 ran flawlessly on the outbound trip for 2 days or about 18 hours while driving and running 1 roof AC Unit. I was plugged in at the campground and did not run the generator for 5 days. I left Sunday for the return trip to Texas and after about 15 minutes the generator voltage output dropped to about 70-80 volts. I spent the day crossing Tennessee with temps in the high 90’s and no AC. Every hour or so I would restart the generator and sometimes had 120 volts for a few minutes and then voltage would drop again. After shutting down and restarting about 10 times during the day the voltage returned to 120 volts and stayed for the next 3 hours.
I unplugged Monday morning from an overnight stop, started the generator and had 120 volts for the rest of my trip which was about 7 hours.
Note: The generator engine speed did not vary during the voltage drops and I have had no previous issues. It has about 550 hours total time with me adding about 150 of those hours.
I know intermittent problems are the most difficult to diagnose so I am looking for suggestions. I was thinking it could be as simple as a loose wire or maybe a voltage regulator issue.
Engine speed determines frequency of output, voltage regulator controls voltage. The regulator may be going bad, or some other problem in the gen set. If it is in warranty, see Onan ---
Mike T
2005 Winnebago Voyage 33V, Workhorse W20, with '06 CR-V in tow, SMI 4 wire Braking system, Blue Ox Underskirt, Pressure Pro.
The capacitor in the voltage regulator is starting to go bad. I'd look around for a new one.
You also might have built up an insulating coating on the brushes and slip rings. Pull the control panel cover and unplug the regulator (12 pin plug). Using an ohmmeter on generator side pin F1 and F2 and you should get between 20 and 26 ohms. If higher, pull the brushes and clean the contact surfaces and then burnish the slip rings back to a copper/brass color.
JimL
Jim & Jane Latour
08 Chevy 3500HD, crew cab, dually, Duramax/Allison
05 Wilderness Advantage AX6 365 BSQS, Onan 3.6KY
Retired AF CMS (E9) Power Generation and Onan RV genset Level III tech
Grand Strand Sams
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