Generac gen set problem

My generator will stumble like that if i do not allow time for the engine to worm up. it has to run for about a min. then it has no trouble what ever.

The roof AC may not start after turning it off and trying to restart it without giving it a 5-10 minute "rest period". Turn AC off before shutting the generator off and switching to shore power or vice versa, give it the rest period before trying to restart the AC. AC units demand a lot of power when starting up, have the microwave and other high current devices like space heaters off when starting the roof AC.

Thanks to all, much great information. I was able to succesfully run the A/c by carefully starting with no load and adding appliances . I did not attempt microwave, as I have had trouble with that tripping breaker historically. Checked air filter and spark arrestor in exhaust, OK. Will check plug. I worry about damage to appliances if gen is not providing proper volts, so I will be conservative.

j-d wrote:
Today it did, Go figure...

Difference in altitude between the two locations?

Difference in outside temperature between the two locations?

Difference in fuel for the generator between the two locations?

Difference in state-of-charge of the coach batteries (hence, charging load on the generator) between the two locations?

Today I did a genset exercise run. Usually just the A/C on HIGH COOL, but today I added Water Heater and Microwave. I didn't expect it to, but it supported all that load, which is right at 30-amps. Yes it Should but No it Hasn't. Today it did, Go figure...

If the Generac is rated at 4000 watts, it should be able to run one roof AC unit and the microwave at the same time. Start generator, start AC fan, let run for a minute, set control to cool and thermostat to 72 degrees and listen for compressor to run, let run for a couple of minutes, then try heating something in the microwave. If you have a line voltage meter check if voltage is in the green or 110 volts with AC and microwave on. If voltage is low, Generac may need voltage adjustment or other repairs. Run AC alone and check line voltage is in the green, if not, don't run AC until you get generator fixed.

Agree with taking this thread to Tech Issues. Also, check smokstak.com, which has space dedicated to Generac gensets.
I can add that our ONAN 4KW unit seems to run fine, but it will not carry as much load as shore tie to a proper 30A campground pedestal. 4KW works out to about 33Amps, so the genset "Should" match a 30A campground pedestal.
The generator won't usually carry both the 15K A/C and the Microwave and campground pedestal usually will. If I had to guess why, I'd venture that the genset has monitoring built into its logic board and that monitoring is very conservative so it cuts off at first sign of voltage or frequency drop. I don't have any kind of energy management system, so campground voltage can sag if it wants to and won't be automatically cut off.

Thanks, will do.

1) Run as few other appliances as you can on AC when you want A/C. Reefer & water heater on propane, etc. Start the A/C fan on low, wait about a minute before putting the thermostat down to where the compressor kicks in (less starting surge).

2) See your owner's manual for maintenance schedule. Maybe the fuel or air filter or spark plug are past due for changing. Also check manual to see if you have a spark arrestor screen in the exhaust that may need cleaning.

3) Ask the moderator to move this thread to the tech forum where some gen techs hang out sometimes.

Jim, "My psychiatrist said I was crazy. I said I wanted a second opinion. He said okay, you're ugly, too."

Thanks for the replies, gen set is a Generac, Guardian RV brand. Model is 40G. As mentioned, it doesn't seem to have the power to run the A/C, but runs the other stuff.