Performed diagnostic on 2000 Carrier. System is not kicking on, error code on thermostat. I cycled system for heat. System initiated heating cycle, but fan never kicked on and system shut off. After carefully troubleshooting system, I found circuit board to be bad as well as indoor blower motor. Both would have to be replaced for it to operate. Went over findings and recommendations. Homeowners are Leaning more towards replacing the system as oppose to repairing it. Repair cost was given to homeowners. Darren will be coming out tomorrow morning to go over replacement options. System is not operational upon departure.