OEM Carrier Pressure Switch 0.18" WC SPST for Model PY4GNAA42090AA

This OEM pressure switch is the factory-specified replacement for the Carrier PY4GNAA42090AA packaged unit. The pressure switch monitors the negative pressure (draft) created by the inducer motor to confirm safe venting conditions before allowing the ignition sequence to proceed. When it fails or sticks open, the control board never receives the "all-clear" signal, resulting in a hard lockout — the system will attempt to start, fail to progress past the inducer stage, and shut down with a diagnostic fault code. Part number HK06WC061 has been superseded by HK06MB061, the current OEM equivalent shipped as a direct drop-in replacement.

• Specs: 0.18" Water Column (W.C.) setpoint | SPST (Single-Pole Single-Throw) | Normally open | Factory-calibrated ±0.01" W.C. tolerance | Replaces HK06WC061 / cross-references Honeywell IS20224-5236
• OEM vs Generic: OEM pressure switches are calibrated to exact W.C. setpoints at the factory. Off-spec generic switches can open/close at the wrong pressure, causing nuisance lockouts or — more dangerously — allowing ignition under unsafe venting conditions.
• Install difficulty: 2/5 — Power down the unit at the disconnect before beginning. Tools needed: flathead screwdriver, needle-nose pliers, and a manometer to verify inducer draft if symptoms persist post-replacement. Photograph all tubing connections before removal; a misrouted hose is the most common post-install error.
• Warranty: 1-year OEM factory warranty. Ships same business day from our warehouse when ordered before cutoff.

Compatibility: Direct OEM replacement for Carrier model PY4GNAA42090AA. Also fits select Bryant and Payne packaged units sharing the same inducer assembly. Always verify the W.C. rating on your existing switch's label before ordering — mismatched setpoints will cause recurring faults. Questions about fitment? Our HVAC parts team confirms compatibility before you order — in stock and ships today.