OEM Carrier Furnace Transformer 120V–24V 40VA for Model PG8MAA042090ADJA

This OEM step-down transformer is the factory-authorized replacement for the Carrier PG8MAA042090ADJA gas furnace, cross-referenced under part number HT01BC116 (superseded by HT680054). The transformer converts 120V line voltage to 24V AC, powering the entire low-voltage control circuit — including the thermostat, gas valve, and control board relay coils. When the transformer fails, the furnace goes completely unresponsive: no thermostat call, no ignition sequence, and no error codes because the board itself loses power. A simple multimeter check between the C and R terminals on the control board will confirm whether your transformer is at fault.

• Specs: Primary Voltage: 120V AC | Secondary Voltage: 24V AC | VA Rating: 40VA | Frequency: 60 Hz | Phase: Single | Mounting: Foot mount | Connection: Wire leads with insulated female quick-connect terminals
• OEM vs Generic: This is a factory-authorized OEM unit shipped in a Carrier/Bryant branded box. Generic transformers often use lower-grade core laminations, running hotter and failing sooner — especially in furnaces with marginal low-voltage wiring that already stresses the VA rating.
• Install difficulty: 2/5 — Shut off power at the disconnect and breaker before starting. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter. Photograph or label all wire connections before removing the old transformer. Match wire leads carefully: primary (120V) to line voltage terminals, secondary (24V) to R and C on the control board.
• Warranty: 1-year OEM manufacturer warranty. In stock — ships same business day from our warehouse when ordered before cutoff.

Compatibility: Direct OEM replacement for Carrier model PG8MAA042090ADJA gas furnace. Also replaces legacy part numbers HT01BC116, HT01BC115, HT01BB126, HT01CT120, HT01BC120, HT01AW115, and additional cross-references — verify your data plate before ordering. Need fitment confirmation? Our HVAC parts team checks compatibility before you buy.