[rsisk]

We did this troubleshooting just last night.

Make sure the ribbon babel to the side car is solid. Replace if necessary.
Make sure the cRIO has power
Remove all connections to the DSC and clear any metal debris
Connect DSC power (should be connected to PDB) and ribbon cable
Check lights on DSC.
Continue adding connections to DSC one at a time until light failure
Investigate problem with last connection added.

Our problem was a two parter; cRIO was not powered (loose power connection would go in and out) and the DIO connection to the compressor pressure switch was wired wrong.