Problems with generator power to coach.

Ok so I will try to explain this clearly, I have done a lot of trouble shooting based on posts I have read here and other sources (manual)  if you have any ideas on what it could be please chime in.  I could be doing something wrong and just not realize it,  This RV is new to me.
2015 Itasca Sunstar 35F 8900mi just picked it up last week.  Its beautiful

I will try to cover this in steps as to what I have done so far.

When I plug into 30amp  everything works fine in the coach.  My "Energy Management system" inside the coach is lit up with all the monitored components (loads) lit up and says 30a

here's the issue when (unplugged from 30amp)
When I start the Generator I hear the clunk of the switch,
On the "Energy management system" inside the coach  all the load lights lite up momentarily and they all go off in quick succession like its shedding the loads one right after the other. 

My Outlets all work, my Microwave works.. but AC/ does not.  Every few minutes all the lights light up again and then go out.  If the AC is set to run it kicks on for a few seconds but shuts off as the "load is shed"

Using a voltmeter I measured the transfer switch voltages in the switch box both before and after I started the generator and the voltage is appropriate per the manual.  There is a green led on circuit board on the generator side of the transfer switch that is illuminated when the generator is on

I checked the two breaker switches on the front of the onan generator and they are both on  I cycled them (with the generator off)

I cycled all the breakers in the box near the door ,  I took off the panel on the breaker box and I know there is a piece of the energy management system in there, it looked fine all screws tight.

So what did I miss, do you have suggestions for me?

Thank you

Greg in Rhode ISland

2015 Itasca/Winn Sunstar 35F

Welcome Greg!  What size is the generator?  Does your EMS indicate current draw when plugged into shore power?  On generator?

John thanks for the response. The generator is a Onan  5500. It has less than 10(ten) hours on it.    When the AC is plugged in the EMS shows current draw that changes as. Power things up and down.  When on generator it shows a # in the readout but as soon as the load sheds meaning all the lights go out. It shows a weird # looks like it has decimals in it.    I know this is a heck of a first post but thank you fr helping me trouble shoot

I think you need to take your unit to a Cummins-Onan dealer and have them load test the generator, then you will know if the problem is external or internal to the generator.  Odds are it is external to the gen set but I think you should start troubleshooting at the gen set and work out from there.

Onan provides a three year warranty
http://www.generatorjoe.net/html/warranty/onanrvwar.html

Sounds like having a power monitor like the P3 P4400 Kill A Watt would be useful to see if the governor on the generator is allowing to much of a speed drop when the load increases.

http://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s01

The previous owner may not have exercised the generator monthly or under sufficient load, at least 50%. Maybe you have jet in the generator carburetor gummed up or a partially plugged fuel filter. Maybe you can try running the generator then gradually increase the load on it by running the microwave, toaster, hair dryer. The infamous hair dryer has caused many exciting incidents when camping. It is a LOAD HOG!!

Before I took it anywhere for repair I think I would look very closely at the automatic transfer switch.

It could be just a little sticky and the contacts may not be getting pulled fully to the generator side. I would also use some very fine sandpaper and touch up the generator side of those contacts. It could be that the first owner allowed the transfer from shore power to generator and back while under load and the contacts are pitted and not making full contact. Or, maybe the generator and transfer switch were not operated very often and the contacts need some attention. Either one could cause an erratic output and possible load shedding.

Make sure shore power is unhooked and the generator is off before you open the transfer switch box and while you work on the switch itself.

Hey Greg.... What did you find out with your generator? We are patiently waiting to hear what the solution was.

sorry I haven't responded back to this thread,  still no resolution,  I have been full timing it in a campground since the end of July hooked to 50amp and haven't needed a gense3t  but I'm about to go on the road soon so I want to get this taken care of.
I talked to a RV local repair guy and he thinks it the auto xfer switch too.    I ordered a new transfer switch and will be replacing it next week.  I'll follow up when I get it working.

Oh Greg, wish you would have stayed with the forum. I'm sure someone would have suggested that you gently force the transfer switch contacts over with a wooden mop handle or dowel or even jumper the contacts to verify the transfer switch.

Most of us would go broke trying to buy every replacement part that an RV tech would like us to try.

Hope this solves the problem.

Hi imgregh,  Are you still there.  I'd love to know what you found.  I have a 2015 Sunstar 35B with the same issue.