Below are instructions for testing the inverters.

Everyone with a Reatta needs the factory service manual to fully understand the Reatta electrical system.  It is a good idea to go through sections 5E, 6, and 8 just to become familiar with everything. For example the inverter schematic is in 8A-88.

Wire Code:
C1 (gray) =12vdc
B (black) = 12 vdc ground
A (white) &  C (blue) =110vac

The inverter is variable so if you put 9v on the input (C1 & B) you should get about 85vac on the output (A & C). (See photo below) This is how it dims.

GM part numbers:
1642274 (black)
1642275 (pink)

Contact:
Endicott Research Group, Inc.
2601 Wayne Street
Endicott, NY 13760
Phone: 800.215.5866
http://www.ergpower.com/

Thanks to Padgett, member of the Reatta forums, for this information.