Carrier 38QB900031 Time Delay HVAC Control Board

Carrier 38QB900031 Time Delay HVAC Control Board is a replacement time-delay relay module used in Carrier furnace and ventilation systems. Identified by part number 38QB900031, this board sits in the control circuit to introduce a deliberate delay between inputs and outputs, coordinating timing of control signals within Carrier equipment that uses the 38QB control family. As a Carrier replacement part, it drops into the unit’s existing control wiring terminal assembly to replace a worn or failed time-delay device without altering the unit’s core control logic. In ventilation and HVAC applications, time-delay relays help manage start-up sequencing and interlock timing, contributing to orderly operation and reducing electrical surges when components engage. The module is designed for installations that specify a 38QB time-delay function and is intended to be installed by qualified HVAC technicians following standard safety practices for electrical components within furnace or air-handler enclosures. Because it adheres to Carrier’s part numbering and connector conventions, it is typically sold as a direct replacement for systems that originally used the 38QB time-delay component, simplifying service and replacement workflows for technicians maintaining Carrier HVAC infrastructure.