OEM Carrier 40VA 120V–24V Step-Down Transformer HT01BC116 for Model PG8UAA042091ACJA

This is the factory OEM step-down transformer for the Carrier PG8UAA042091ACJA gas furnace, sold under OEM part number HT01BC116 (superseded by HT680054). The transformer converts 120V line voltage to 24V AC to power all low-voltage control circuit components — including the thermostat, gas valve, inducer relay, and control board. When this transformer fails, the furnace loses all 24V control signal: the thermostat goes blank, the system won't call for heat, and no safety functions respond. It's one of the first components to check when you have a completely unresponsive furnace.

• Specs: 40VA rating | 120V primary | 24V secondary | 60 Hz single-phase | Foot-mount style | Wire lead connections with insulated female quick-connects
• OEM vs Generic: This OEM-spec unit is factory-matched to the control board's load requirements. Generic transformers frequently run undersized VA tolerance or use inferior core materials, leading to overheating, voltage sag, and premature failure — particularly when the furnace is paired with a central AC system sharing the same 24V circuit.
• Install difficulty: 2/5 — Disconnect power at the breaker and verify 0V before touching any wiring. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to verify 24V output post-install). Photograph all wire connections before disconnecting. Check between the C and R terminals on the control board after installation to confirm 24V output.
• Warranty: 1-year OEM manufacturer warranty. In-stock units ship same business day from our warehouse.

Compatibility: Designed as the direct OEM replacement for Carrier model PG8UAA042091ACJA gas furnaces. Note: OEM part number HT01BC116 has been factory-superseded by HT680054 — both are genuine Carrier authorized parts and direct drop-in replacements. Also replaces HT01BC115, HT01BB126, HT01CT120, HT01BC120, and related cross-reference numbers. Confirm your unit's control voltage requirement on the data plate before ordering. Our team is happy to verify fitment — reach out before you buy.