My generac 5500 starts and runs fine but it produces no voltage. fuses are not tripped.

have the unit checked by an authorized generator repair shop
if it was operating when shore power came back on there is every possibility that the generator or inverter has been damaged from the lack of synchronization of the sine wave

I has this problem after performing Schedule A maintenance. Called Generac. They advise this a trip caused by removing the fuse before work to prevent engine start up, The fix is to turn unit in off position and then press ENTER key.

There are several Generac forums available:

generac forum Bing

check voltage input at voltage regulator, then check output from
the regulator.

With the engine off, check the exciter brushes and slip rings which supply magnetic power for the alternator winding in the stator. Also, check the motor-to-alternator mechanical coupling. Check the breakers for tripping. To service beyond this point requires a schematic of the alternator, a voltmeter, plus knowledge of what the schematic is telling you. Good luck!

First check with the dealer and see if it is still under warranty. If it is not, make sure nothing is blocking the air flow around where the control modules are located. This could cause the voltage regulator and other electronic parts to overheat. Next check the brushes and make sure they are free of any dust or build up preventing them from making contact.

If everything is OK the next thing I would do is change the voltage regulator.

What about when you have it powering the motorhome, without AC on, does it trip then? Do you have anyone you know with a multimeter and knows how to use it? How about buying a plug in voltage meter at a hardware store as a good start. You simply plug it in to a receptacle in your motorhome and it will tell you the incoming voltage and they are not very expensive. That will help diagnose generator problem.

Remove front cover on the genset and you will see the brushes and rings. Clean the rings if black with emory cloth and inspect brushes. Flash the fields by apply a 12V battery to the brushes. the brush closest to you or the bearing is connected to the positive side of battery and the back brush is negative. You have to do this with genset running. You should notice your voltage climb up to over 50Vac maybe even over 100Vac. Make sure to use rubber gloves when flashing fields and keep hands away from rotating parts. if voltage does increase when flashing the the voltage regulator is shot. If voltage does not climb then you will need a new genset or generator end.

when power tools get old they draw more amperage. 6.8 amps new might be 8 amps. over loading when older.

The problem is that the printed circuit board inside the generator draws a little current from the battery even when the generator is not running. Over the course of a few days this can make the battery weak enough to be unable to get recharged by the built in running charger which results in not enough power to run the electronic governor on the generator. Usually the spark plugs will work even with a fairly low battery.

Most of the Generac generators come with a built in trickle charger that runs off of the transfer switch load terminals. If your built in charger isn't doing the job it's either broken or you have the wrong sort of battery installed in the generator.

Regards,
Carl