Both Air Conditioners Don't Work

Both of our roof top Duo-Therm air conditioners work on Fan Only. Compressors don't start when set to run. Duo-Therm Comfort Control Center (5 button). Circuits are in tract (fans work) Had the capacitor checked on one unit and they said it was okay. Seems like the only thing in common with both units is the control center. How do you check the Comfort Control Center to see that it is sending the signal to the ac,s to engage? Should I look elsewhere? Suggestions?