Tempstar Low Pressure Switch Assembly for T4H424GKD100 — Refrigerant Safety Switch | Ships Today

Overview

This OEM low pressure switch assembly (part number 1177594) is the refrigerant-side safety control on your Tempstar T4H424GKD100 heat pump. Wired into the 24V control circuit, it continuously monitors suction-line pressure and opens to shut the compressor down if pressure drops below a safe threshold — protecting the compressor from running on a low or lost charge, a blocked metering device, or a frozen evaporator. Without a working low pressure switch, a slow refrigerant leak can let the compressor run dry and self-destruct. The switch is a sealed assembly that mounts on the suction line; over time the contacts can stick open (preventing the unit from ever starting) or weld closed (defeating the protection it's there to provide). It is an inexpensive part that guards a very expensive compressor.

Specifications

Compatibility

Factory-specified for the Tempstar T4H424GKD100 heat pump and shared across matching ICP-family outdoor units (Heil, Comfortmaker, Arcoaire). Confirm the cut-out/cut-in pressure settings and the connection fitting match your original switch before installing.

Installation Guide

1. Safety First — Disconnect power at the disconnect and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the service panel and locate the pressure switch on the suction (low-side) refrigerant line.
3. Document — Photograph the two control wires and the switch's mounting position.
4. Remove — Disconnect the 24V leads; if the switch threads onto a Schrader-style port it can be replaced without recovering charge, otherwise recover refrigerant per EPA rules before opening the line.
5. Install — Thread on the new switch (replace the port core/seal if required), then reconnect the control leads per your photo.
6. Test — Restore power, confirm the switch is closed at normal pressure, and verify the compressor starts and runs.

Signs You Need a Replacement

• Compressor won't start even though charge and pressures are normal (switch stuck open).
• Unit short-cycles or nuisance-trips on the low pressure circuit.
• No loss-of-charge protection — compressor runs on a low charge.
• Corroded terminals or refrigerant weeping at the switch body.

Shipping & Returns

Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.