Generator will not power the lights?

Yellow is likely a battery issue. Low battery voltage or not charging, failed battery, etc.

These units require schedule maintence. Go to

https://www.generac.com/service-support/product-support-lookup

Find model installation operation manual and familiarize yourself with the system or pay the service tech.

When you have a generator with a inverter in it you have to be careful of overloads an static electricity. More than likely one or more otf the MOSFETs has blown. An inverter is really a switching supply. Not very hard to replace parts but if you have spme skill with electronics take it apart an give it a go. If transistors have not blown you may find a blown fuse inside on circuit board. You will never find a schematic for any of these units. They are protected because the dealers pay to much for selling rights you cant hardly get them. But i would take it apart an see what you have. Or find a good electronics guy an ask him to check it

The problem with the repair service is another matter. Emergency generator and it's switch gear are there for emergency purposes. It has to be exercised periodically. The switch gear should have a toggle switch to simulate a power outage. the switch cuts power to the sensor sensing power from the utility company. This tells the switch gear that power was lost, start the engine and switch over to generator power. Run for a period where engine reached running temperature and switch back to stand by to shut down. Do this periodically, and be grateful the event was not a disaster. Think of your back up electrical system as the spare tire of your car and similar equipment and enjoy your investment. Good people brings you happiness, bad people brings you experience !.

check that the over load switch is not seized of course then replace

Check all the fuses. Sounds like the inverter section has gone south

Switch generator to off. Remove 7.5A fuse. Disconnect Negative (-) battery terminal first and then Positive terminal (+). slide battery out the front (may be a tight fit) and install the new battery reversing removal steps. Connect (+) first and (-) last. Reinstall 7.5A fuse and switch to manual to start and test run.

batteries only last about 3 months on these units. make sure you are within 20 ft of the generator and put in new batteries. The green light will blink is a minute or so.

Sounds like a problem with the H-100 controller. Contact Generac to get support.

fuse are meant to protect the costlier part of the machine thereby damaging itself.  there is probably overloading of your circuit. call the electrician and find the actual power required by your house.  there is a possibility of having a short circuit in your generator. your local electrician can check it.