OEM Carrier 40VA Control Transformer for Model C4850C50AJ02051

This OEM control transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C50AJ02051 packaged unit. The transformer steps down line voltage (120V) to the 24V signal voltage required by the thermostat, control board, contactor coil, and all other low-voltage control circuit components. When this transformer fails, the entire control circuit goes dead — your thermostat shows no power, the system won't respond to any call for heating or cooling, and a multimeter at the secondary terminals will read 0V instead of the expected 24–28V.

• Specs: 40 VA rating | Primary: 120V | Secondary: 24V | Class 2 control transformer | OEM part number HT01BD236 | Factory foot-mount configuration
• OEM vs Generic: This is the genuine factory OEM unit built to Carrier's exact VA rating and insulation class. Generic transformers frequently run under-rated VA, causing thermal overload failures within one season — especially in multi-stage or heat pump systems drawing close to the transformer's full capacity.
• Install difficulty: 2/5 — Shut off all power to the unit at the disconnect before beginning. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter, wire nuts or spade connectors. Label all wires before disconnecting. Verify fuse or breaker on the 24V secondary circuit before condemning the transformer.
• Warranty: 1-year OEM factory warranty against defects in materials and workmanship. Orders placed before 3 PM EST ship the same business day from our warehouse.

Compatibility: Designed for the Carrier C4850C50AJ02051 packaged unit. Before ordering, confirm your existing transformer's VA rating and primary/secondary voltages on the unit's wiring diagram or data plate. OEM part number HT01BD236 can be cross-referenced directly for a confirmed fit. Need help verifying compatibility? Our HVAC parts specialists confirm fitment before you order — no guesswork.