Stephen,
If you have not done so yet, you need to go to the following Van’s download web page:
https://www.vansaircraft.com/downloads/#ElectricalSystemDiagrams
Then download the PDF electrical diagram titled:
RV-12 SV-AP-KNOB ELECTRICAL SYSTEM (Finish Kit Shipped after 08-25-11)
I would first start by verifying the 2 amp fuse for the trim circuit is good. Then move on to the actual wiring.
Looking closely at the drawing, you will see the trim switch is part of the AV-50001 Switch and Fuse module and the 22 gauge wires associated with trim up and down are PTRIM SW+ and PTRIM SW- they are on pins 19 and 18 and labeled F2034 and F2035 respectfully. Those two wires get wired directly to pins 3 & 4 on the Dynon AP Control Panel.
The trim power is 18 gauge wire assigned the label of F2030 and is wired directly from pin 15 on the AV-50001 module to pin 9 on the Dynon AP Control Panel.
After the rewire, follow the SkyView trim setup procedure so trim movement and takeoff trim position can be established.
You will end up with the instrument panel trim switch wired directly to the pilot trim input (pins 3 & 4) on the AP Control Panel. Moving the trim switch will place a ground on either pin 3 or 4 depending on which way you moved the trim switch. Should you ever decide to also install a trim switch(s) on your control stick grip(s) tie those two wires to the co-pilot inputs on pins 5 & 6 of the Dynon AP Control Panel.
As a side note: Dynon has assigned the priority so the pilot input will override the co-pilot input. This means should your stick mounted trim switch(s) become compromised, the instrument panel trim switch will override the stick mounted switch(s).
Once it is all wired correctly, and the SkyView autopilot setting is optioned for the
expert mode, the system works great! When autopilot is engaged, the AP Control Module will make trim adjustments automatically ... you will hear a SkyView audio announcement "trim nose up" or "trim nose down" and the AP Module just does it for you. There is also a menu setting in the SkyView that allows you to make the trim less sensitive at higher cruse speeds. I'm very pleased with my Dynon AP Module.
Hope you find the above helpful.