OEM Carrier Draft Inducer Pressure Switch 0.18" WC for Model PY4GNAA30040AA

This OEM draft pressure switch is the factory-specified replacement for the Carrier PY4GNAA30040AA packaged unit. The pressure switch proves that the inducer blower is creating sufficient negative pressure before allowing the ignition sequence to proceed. When this switch fails or sticks open, the control board cannot confirm safe draft conditions, resulting in a hard lockout — the furnace or heat section will attempt to start and then shut down without ever reaching ignition. Symptoms include a no-heat call with the inducer running but no spark or gas valve opening.

• Specs: 0.18" WC (inches water column) set point | Normally open, closes on negative pressure | Single-port hose barb | Factory-authorized Carrier/Honeywell design | Cross-references: HK06WC061, HK06MB061, Honeywell IS20224-5236
• OEM vs Generic: OEM pressure switches are calibrated to the precise 0.18" WC trip point required by this unit's control board. Off-brand switches frequently drift in tolerance, causing nuisance lockouts or — more dangerously — failing to detect a blocked flue condition.
• Install difficulty: 2/5 — Disconnect power and gas before servicing. Tools needed: 1/4" nut driver, flat-head screwdriver, manometer (to verify draft post-install). Label or photograph the pressure tubing port before removal. Swap the hose to the new switch and confirm the spade terminal connections are fully seated.
• Warranty: 1-year OEM manufacturer warranty. Ships same business day from our warehouse when ordered before cutoff.

Compatibility: Fits Carrier model PY4GNAA30040AA packaged unit. Also cross-compatible with select Bryant and Payne models sharing the 0.18" WC pressure switch specification — verify against your unit's data plate and wiring diagram before ordering. Note: OEM part number HK06WC061 has been superseded by HK06MB061; both are fulfilled as the current production version. Questions about fitment? Our HVAC parts specialists verify compatibility before you order.