I am posting this for others who may have the same issue. I looked through all of the generator threads on this forum and other forums and did not find the fix that was so simple.
Hopefully this will help someone to not go through what I did. It was such a simple fix.
The way I found the fix was by searching on “Onan generator forums”. I found one link that took me to a page where an Onan tec was talking someone through things to check.
Generator – 2007 Marque Gold 5500 Carbureted
Initially the generator would shut down whenever I turned off one of the AC units. Then it got to where it would run about 2 minutes on a cold start and then it would shut down and every 6 seconds after.
It was giving error code 14 which states:
HIGH AC FREQUENCY—CODE NO. 14 (After the starter was engaged Frequency jumped to more than 70 Hz for 40 milliseconds or to more than 2% over nominal for 6 seconds)
1. Check for a tripped generator set circuit breaker, reset if necessary, and run with fewer loads. (A breaker tripping under load can cause generator set frequency to overshoot.)
2. Check all fuel fittings and filters for fuel and air leaks and tighten as necessary. (Air bubbles can disrupt frequency.)
This led me to believe it was a fuel issue. I changed the fuel filters and fuel pump to no avail. Checked all fuel lines, nothing.
It was due to running at too high RPM. I adjusted the governor a quarter turn at a time. It took 6 quarter turns (1.5) to get to stay running. Running with both AC and when I shut one off it continues to run. I am a happy boy.