My Generac generator is running but not supplying power in house. What could be the problem?

SOURCE: Generac Guardian 17.5KW Generator dies

If this is one of the big "taco cart" portables you need to check that the vent on the gas cap is open when you're running the engine. In the center of the gage on the gas cap is a little knurled knob, turn it counter clockwise (lefty loosey), about a half turn or so and run the generator.
If that doesn't solve your problem add to it here, otherwise please give me a rating I'm trying to build a little credibility here and could use the help.
Carl

SOURCE: Generac Guardian 15kW Generator

That sounds just about right, if the relay contacts get welded together it sometimes takes out the driver on the printed circuit board. As you found out, 12vdc from 23 to 194 makes the transfer switch move to the Generator position, relay not energized makes the ATS move to the Normal position.

You can make a nice test function by installing a 10 amp contact switch in series with either the N1 or N2 terminals. When the switch is open the generator thinks the Normal power has failed.

Regards,
Carl

SOURCE: 10kw Generac shut down overspeed

Make sure that the throttle linkage is all there and not damaged/misadjusted, then get a manometer and check your inlet gas pressure. Gas pressure should be 8 inches of water column and stay there running or not.

Carl

SOURCE: I have a 17kw generac generator that will run

I have the 18KW model and was told that most alarms relate to a low battery. Make sure the battery charger in the Transfer Switch is properly feeding the battery or hook up a mobil battery charger to the battery and see if the alarm goes away. Good Luck.