OEM Carrier 40VA Control Transformer HT01BD702 for Model C48A905064

This OEM control transformer (part number HT01BD702) is the factory-specified replacement for the Carrier C48A905064 packaged unit. The transformer steps down line voltage (120V) to 24V AC to power the entire low-voltage control circuit — including the thermostat, contactor coil, and control board. When this component fails, the system goes completely unresponsive: the thermostat goes dark, the unit refuses to cycle, and no control signals reach any downstream component. If your system is totally dead with no error codes and you've already ruled out a tripped breaker, a failed transformer is the most likely culprit.

• Specs: 40VA capacity | Primary: 120V AC | Secondary: 24V AC | Factory-matched OEM construction | Replaces OEM part number HT01BD702
• OEM vs Generic: This is the factory-original Carrier transformer engineered to exact VA and voltage tolerances for the C48A905064. Generic transformers can run underrated VA, causing overheating and premature failure — especially under heavy thermostat demand or multi-stage control loads.
• Install difficulty: 2/5 — Shut off all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to confirm 24V output after install). Label or photograph all wire connections before disconnecting. Check for a blown fuse on the secondary side as a root cause before replacing the transformer.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Engineered specifically for the Carrier C48A905064 packaged unit. Always verify your existing transformer's primary voltage, secondary voltage, and VA rating against your unit's data plate before ordering. If you have questions about fitment, our HVAC parts specialists are available to confirm compatibility before you buy.