Could use some generator help

On my 1995 Generac when I turn on an air conditioner the generator has to dig in to stay running. There is definitely a throttle increase. On my son's Onan when the air conditioner is turned on the generator stops. This has led me to think it's the governor.

The engine is not operating at the correct speed to maintain voltage and frequency.
That is if the OP's frequency is a typo. If it is not a typo then the voltage regulator is suspect.
I replaced mine with one from Flight systems

The throttle linkages may need a little WD-40. Good luck.

An ideal generator of the common generator type the motor will run at a constant speed, 3600 RPM, 2400 RPM and 1200 RPM are common engine speeds, (others are possible) but it should be locked on that speed and never change Oh they do, but they should not.

Sound will change, becoming deeper and throater as load increases, but speed should NEVER change on a traditional generator.

(A sudden change in load may make it surge or dip but it should quickly return to 3600 or something that relates to it (2400, 1200 and such)

INVERTER generators like the famous Honda EU-#000i series, those the engine changes speed with load, But not the traditional generator.

As others have said, though... you do have a problem, i am guessing the voltage regulator BUT I STRESS THE WORD GUESSING!!!

does the engine slow down a little
or Hold steady
if the engine slows down, then it could be a Governor issue
IF the speed holds even .while the voltage drops, then it is in the voltage regulator section of the control board
and it likely needs a new control board

the governor is mechanical and unless the linkage is sticky, very little goes wrong, unless a spring breaks in the linkage.. which often results in Hunting aka speed variation

control board failure happens more than governor failure

you will find some troubleshooting guides at
http://www.flightsystems.com/troubleshooting/

Thanks guys

I assume that's a typo for 60 Hz (rather than 6 Hz) at startup.

The governor should keep the engine speed pretty much steady, not varying greatly with load. Generator frequency, assuming it's not an inverter generator (which most or all RV generators are not), is directly tied to the engine speed; if it's 60 Hz ± a bit, the governor is operating properly.

This sounds to me more like a failure in the voltage regulation system. The "Tech Issues" forum is where you'll most likely find generator experts here; maybe some kind moderator can move this thread over there.

Voltage and frequency is adjusted by engine speed in some older units. Should be near 130 volts and 60-62 on frequency.