OEM Carrier Control Transformer 40VA 208/230V to 24V for Model SUBCLR50HJ403012

The Carrier HT01BD209 is the factory OEM control transformer for the SUBCLR50HJ403012 HVAC unit. Its sole job is to step down line voltage from 208/230V to a stable 24V supply that powers every low-voltage component in your system — the thermostat, control board, contactor coils, and safety circuits. When this transformer fails, the result is total control-circuit collapse: the thermostat goes dark, the system won't call for heating or cooling, and no fault codes appear because the board itself has no power. A blown fuse on the secondary side is often the first clue; a failed transformer is the frequent culprit.

• Specs: 208/230V Primary | 24V Secondary | 40VA rated | 50/60 Hz | Genuine Carrier OEM — Part No. HT01BD209
• OEM vs Generic: This OEM unit is wound to exact Carrier factory tolerances, ensuring stable 24V output under full VA load. Generic transformers may deliver fluctuating secondary voltage that causes nuisance lockouts, intermittent thermostat dropouts, and premature control board failure.
• Install difficulty: 2/5 — Shut off all power at the breaker before beginning. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter (verify 0V before touching terminals). Photograph or label all low-voltage wiring before disconnecting. Replace any blown secondary fuse at the same time.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Direct OEM replacement for Carrier model SUBCLR50HJ403012. Also replaces superseded Carrier part numbers HT01BD207, HT01CN232, and 9076-00. Verify your unit's data plate confirms 208/230V primary input before ordering. Have a fitment question? Our HVAC parts specialists confirm compatibility before you buy — ships same day so your system is back online fast.