OEM Carrier Furnace Transformer 120V to 24V 40VA — Model U19X125U48B (HT01CN001)

This is the factory OEM replacement transformer for the Carrier U19X125U48B HVAC system. The transformer steps down 120V line voltage to a safe 24V (with 12V tap) to power all low-voltage control circuits — including your thermostat, contactor coil, control board, and zone valves. When the transformer fails, the entire control circuit goes dark: the thermostat loses power, the system refuses to start on any call for heating or cooling, and you may notice a faint burning smell or audible buzzing from the transformer itself.

• Specs: 120V primary | 24V / 12V dual secondary | 40VA rated | Factory-matched OEM part number HT01CN001 | Replaces legacy part numbers HT01BJ115, 19EA41612, 19EA42612
• OEM vs Generic: This is a genuine Carrier OEM transformer wound to exact factory VA and voltage tolerances. Generic transformers can run under-rated VA, causing premature overload failure, nuisance tripping of the internal fuse, or erratic thermostat behavior — especially on systems with multiple zones or communicating controls.
• Install difficulty: 3/5 — Turn off all power at the disconnect and breaker before starting. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter, wire nuts or terminal screws. Label all low-voltage wires (R, C, G, W, Y) before disconnecting. Verify 24V output with a multimeter before reassembling the panel.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our warehouse.

Compatibility: Designed as a direct drop-in replacement for the Carrier U19X125U48B unit. Verify your unit's data plate shows a 120V primary / 24V secondary control circuit and 40VA rating before ordering. Cross-references include HT01CN001A and Standex Electronics FT3746. Questions about fitment? Our HVAC parts specialists verify compatibility before you order — call or chat today.