Had it on some forest roads. Wash board, rock, etc. It shook the vehicle a bit and I lost a fair amount of electrical all at once.

Turn Signals (hazard lights still work)
Trailer Brakes
Rear A/C
Heated Seats
Cruise Control

Probably some other issues I'm forgetting.

I usually perform most repairs myself, but electrical is getting more and more complicated. Called my local Ford dealer to do some diagnostics and can't get an appointment for at least 2 weeks.

Pulled and inspected the fuses related to the dead systems, they looked ok, no blown fuses.

I unbolted the fuse panel, turned on the ignition, activated the non-working turn signals, and turned on the non-working rear air. Wiggled and pushed each connector on the back of the fuse panel to see if I could get either to start working. No luck. Looked around under the dash for loose connections, didn't see any, but it's pretty busy under there.

Spent a fair amount of time searching and reading about electrical issues on this site. My 2005 has a different fuse panel than the earlier ones with the GEM on the back that was prone to water damage from windshield leaks.

I'm not sure where to start. Anyone have a strategy or some techniques that could help me track down the problem? Wiring diagrams? Locations of all the grounds?

It's a 2005 Excursion Limited 6.8 4x4. Had it 11 years, 202k.

Any help or advice much appreciated.

 

the turn signals and trailer brakes makes the connector to your multi function switch suspect. It is a known failure point.

A quick 15 minute job to pull the plastic shroud around the steering wheel to check it out. The tang holding the connector in place fails. Some creative zip tie work takes care of the issue.

Consider picking up a wiring diagram if you are going to dive in deeper

 

In addition, if you have the plastic cover off on the steering column, check for the known chafed wire issue.

 

Popped the lock cylinder and removed the steering column shroud. Checked all of the connectors, everything tight and locked in. Tried wiggling the connectors while activating turn signals, didn't get a blink.

Wiring diagram on the way. Any other suggestions? Owners manual doesn't label the relays in the fuse panel. I would think rear air and heated seats might be run through a relay.

 

Also looked for evidence of wiring damage/chaffing. Didn't see any.

 

Other then grounds which you mentioned I got nothin. But a loose or bad ground would or could certainly account for your symptoms