HVAC stuck on defrost

Was an HVAC reset protocol ran after the new parts were installed?

If this is a vacuum actuator the system has lost vacuum. When this happens it defaults to defrost for safety reasons. Look for a broken or disconnected vacuum hose at the intake manifold or firewall. Also, check that, with the actuator disconnected the door moves freely. Some of these doors were prone to breakage and the whole heater box needs to be removed to replace the broken door. Jim

Do you have automatic or manual control? The actuators are different for the different controls. The automatic has a digital display.