OEM Carrier Control Transformer 40VA 120V/24V for Model HA1BJX042000ABAA

This OEM control transformer (part# HT01AW229) is the factory-specified replacement for the Carrier HA1BJX042000ABAA unit. The transformer steps down 120V line voltage to the 24V AC signal required to power the thermostat, control board, and all low-voltage control circuits. When the transformer fails, the entire control circuit goes dead — the thermostat goes blank, the system stops responding to calls for heat or cooling, and nothing operates. This is often the first component to suspect when the system is completely unresponsive despite having line power.

• Specs: 40VA rating | Primary: 120V AC | Secondary: 24V AC | OEM part number HT01AW229 | Factory-matched electrical characteristics for reliable low-voltage circuit performance
• OEM vs Generic: This OEM transformer is wound to Carrier's exact VA rating and insulation class. Generic transformers frequently run underrated VA, causing overheating, nuisance tripping, and premature control board failures due to voltage sag under load.
• Install difficulty: 2/5 — Shut off all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter. Confirm secondary output voltage (should read ~24–28V AC) before reconnecting control wiring. Photograph all wiring connections before removal.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our warehouse.

Compatibility: Engineered specifically for the Carrier HA1BJX042000ABAA. Always verify your existing transformer's VA rating and primary/secondary voltages against your unit's data plate before ordering. If your control board repeatedly blows fuses or trips, inspect the transformer secondary for shorts before replacement. Our fitment team is available to confirm compatibility before you order — same-day shipping available on all in-stock OEM parts.