OEM Carrier 40VA Control Transformer for Model C4850C48AY03661

This OEM Carrier control transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C48AY03661 packaged unit. The transformer steps down 120V line voltage to the 24V signal required by your thermostat, contactor coil, and control board. When this component fails, the entire low-voltage control circuit goes dead — the thermostat goes blank, the system stops responding to calls for cooling or heating, and nothing operates. Replacing a failed transformer is one of the most cost-effective repairs in HVAC service.

• Specs: 40VA rated | Primary: 120V | Secondary: 24V | OEM part number HT01BD236 | Factory-matched to Carrier C4850C48AY03661 wiring harness and mounting bracket
• OEM vs Generic: This is a genuine OEM Carrier transformer manufactured to exact VA and voltage tolerances. Generic transformers frequently underperform at rated load, causing nuisance tripping of the secondary fuse and premature control board failure — especially in packaged units with higher 24V circuit demands.
• Install Difficulty: 2/5 — Disconnect all power before servicing. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (verify 0V before touching terminals). Photograph all wiring connections before removal. Secondary fuse should also be inspected and replaced if blown.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our climate-controlled warehouse.

Compatibility: Engineered specifically for the Carrier C4850C48AY03661 packaged unit. Always verify your existing transformer's VA rating and primary/secondary voltages against your unit's data plate before ordering. If your secondary fuse blew, diagnose the root cause (shorted wiring or failed component) before installing to protect the new transformer. Our HVAC parts specialists are available to confirm fitment — just reach out before you order. In stock — order by 3PM and ships today.