On Tuesday, December 19, 2017 at 5:35:25 AM UTC-5, Danny D. wrote:
Normally the Generac generator feeds the whole house.
No fuse is tripped and I switched them all anyway (like everyone does).
What would make a generator only feed half the house? (if that)

At first it wouldn't go on automatically - so that may be a clue.
I had to switch it to automatic from manual and after a dozen of those
switches, it went on automatically.

I'm wondering how to debug the transfer switch but I opened both up and
they seem to be the same with no moving parts.

Any ideas?

Just get a meter and start tracing back the hot leg that has no voltage.