OEM Carrier 40VA Control Transformer HT01BD702 for Model C48A603564

This is the OEM factory-specified control transformer (part number HT01BD702) for the Carrier C48A603564 packaged unit. The transformer steps down 120V line voltage to 24V AC to power the entire low-voltage control circuit — including the thermostat, contactor coil, and control board. When this transformer fails, absolutely nothing responds: the thermostat goes dark, the system won't call for cooling or heating, and no fault codes appear because the control board itself has lost power.

• Specs: 40VA rated | Primary: 120V AC | Secondary: 24V AC | Factory-matched OEM replacement | Part number HT01BD702
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances required by Carrier's control circuit. Undersized or off-tolerance generic units can overheat, blow the secondary fuse, or fail to sustain voltage under full control circuit load — leading to nuisance lockouts and repeat failures.
• Install difficulty: 2/5 — Disconnect power at the breaker and confirm voltage is absent before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter. Photograph or label all wiring connections before removing the old transformer. Check and replace the 3A or 5A secondary fuse if blown — a failed fuse often indicates the transformer itself has failed.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our warehouse.

Compatibility: Designed as a direct OEM replacement for the Carrier C48A603564 packaged unit. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate or transformer label before ordering. Our fitment team is available to confirm compatibility prior to purchase — same-day shipping on all in-stock orders.