Large fan will come on as required by the AVR. It is powered by the aux power supply which is powered by the gen (11s and 44s). You are in a Catch-22 position. The aux power supply could be externally excited to see if it produces 11-12 VDC. You MUST disconnect 11s and 44s from it first. The fan could be externally excited with 12VDC to see if it runs. If they both check out, you probably have an issue in the AVR.
VSCF Gate Fault probably refers to the gate (control) terminal of an SCR or Triac - a transistor-like device mounted on the heat sink and cooled by the fan.
I didn't have a ton of time this week - but I did confirm that the aux power is working fine (tested manually), and that there are no issues with the alternator i.e., I did all of the wiring tests in the manual related to the brushes and windings etc.
So, it is narrowed down to the avr. Looking into the IGBT and the driver - but don't know if I will pursue it or not. Really there are two options there: send it out to have the components replaced or try to do it myself. I'm trying to get an estimate from a local pcb shop. The IGBT itself is only $60, the driver is probably a lot less. I'd prefer to send it out as my soldering skills are pretty weak - but can only do that if it's affordable - really comes down to the cost.
At this point, about 8 hours total were spent and $180, that includes transporting the generator and buying lunch for my buddies who helped me move it.
I am trying to locate schematics for the avr - they seem hard to find - but if anyone has them it would be greatly appreciated.