What part is failing in a 1999 Chrysler Cirrus when the dashboard controls auto-door locks air conditioning and alarm all stop working?

The most likely culprit when all those dashboard controls (auto-door locks, A/C, and alarm) fail simultaneously in a 1999 Chrysler Cirrus is a faulty Totally Integrated Power Module (TIPM).

The TIPM is a central control module that manages many electrical functions in the vehicle. Its failure would explain the widespread loss of functionality you're experiencing. While other issues *could* cause some of these problems individually, the simultaneous failure strongly points towards the TIPM.