OEM Carrier 40VA Control Transformer HT01BD236 for Model C4850C50Z2030500

This OEM control transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C50Z2030500 packaged unit. The transformer steps down 120V line voltage to the 24V AC signal that powers your thermostat, control board, contactor coil, and all low-voltage safety circuits. When it fails, the entire control circuit goes dead — the thermostat goes blank, the system makes no response to calls for heating or cooling, and no error codes are generated because there is no power to generate them. It is one of the most commonly overlooked failure points in any HVAC diagnostic.

• Specs: 40VA rated | 120V primary / 24V secondary | Replaces OEM part# HT01BD236 | Factory-matched output voltage tolerance for stable low-voltage control circuits
• OEM vs Generic: This is a genuine OEM Carrier transformer wound to exact factory specifications. Generic transformers frequently exhibit voltage sag under load, which causes intermittent contactor chatter, nuisance lockouts, and premature control board failures — costs that far exceed the small savings at purchase.
• Install difficulty: 2/5 — Shut off all power to the unit at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter (to confirm 24V output after install), wire nuts or spade connectors. Label all wires before disconnecting the old unit. Replacement typically takes 20–30 minutes.
• Warranty: 1-year OEM factory warranty against defects in materials and workmanship. In-stock and ships same business day from our warehouse.

Compatibility: Designed for the Carrier C4850C50Z2030500 packaged unit. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate or wiring diagram before ordering. Need help confirming fitment? Our HVAC parts specialists verify compatibility before you buy — no guesswork, no returns.