OEM Carrier Control Transformer 40VA 120V/24V for Model C48A904064 — Part HT01BD702

This OEM replacement control transformer (part number HT01BD702) is the factory-specified unit for the Carrier C48A904064 packaged system. The transformer steps down 120V line voltage to the 24V AC signal that powers your thermostat, contactor coil, and all low-voltage controls. When it fails, the result is total control circuit loss — your thermostat goes blank, the system won't respond to any call for heating or cooling, and nothing works. A failed transformer is often misdiagnosed as a bad thermostat or control board, making correct identification critical before replacing costlier components.

• Specs: 40VA rating | 120V primary / 24V secondary | Class 2 control transformer | Direct OEM replacement for part number HT01BD702
• OEM vs Generic: OEM transformers are wound to exact VA and impedance specifications for your Carrier unit. Undersized or off-spec generic transformers can blow fuses repeatedly or fail to sustain 24V under full control circuit load, leading to nuisance lockouts.
• Install difficulty: 2/5 — Disconnect all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter. Test primary voltage before install and verify 24V output after. Always label wires before disconnecting old transformer leads.
• Warranty: 1-year OEM factory warranty. Orders placed before cutoff ship same business day from our stocked warehouse.

Compatibility: Designed for the Carrier C48A904064 packaged unit. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate or wiring diagram before ordering to confirm fitment. Our parts specialists are available to verify compatibility before you purchase — no guesswork required.