OEM Carrier 40VA Control Transformer for Model C4850C48ZN035200

This OEM step-down transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C48ZN035200 packaged unit. The transformer converts 120V line voltage to the 24V AC signal that powers your thermostat, control board, contactor coils, and all low-voltage safety circuits. When it fails, the entire control circuit goes dark — the thermostat shows no response, the system won't initiate a heating or cooling call, and nothing works regardless of thermostat settings. A failed transformer is often misdiagnosed as a bad control board, making this a critical first-check component.

• Specs: 40VA rating | Primary: 120V AC | Secondary: 24V AC | OEM Part# HT01BD236 | Factory wire leads for direct reconnection
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances required by the Carrier C4850C48ZN035200 control circuit. Undersized or off-tolerance generic transformers can overheat, blow fuses repeatedly, or cause nuisance lockouts that are difficult to diagnose.
• Install difficulty: 2/5 — Disconnect power at the disconnect box and verify zero voltage with a multimeter before beginning. Tools needed: flathead and Phillips screwdrivers, wire nuts or terminal connectors, multimeter. Label or photograph all wire connections before removal. Check for a blown 3A or 5A control fuse on the board — a shorted transformer often takes the fuse with it.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our warehouse.

Compatibility: Designed for the Carrier C4850C48ZN035200 packaged unit. Verify your existing transformer's VA rating and primary/secondary voltages on the data plate or wiring diagram before ordering. If you're unsure of fitment, our parts specialists can verify compatibility before you purchase — same-day shipping available on all in-stock OEM parts.