Our Glendale CA a/c technician returned to a retailer to complete needed repairs. Their Trane unit needed a new RTRM board that we had ordered in prior to this visit. After wiring in the new board, our technician powered on the system and found the compressor still not powering on. Continued troubleshooting, found a connection disrupting the stage 2 compressor. Removed and capped it. Reset system again and confirmed unit is now operational.