SLP5090 – REFRIGERANT LOW PRESSURE SWITCH (OPEN @ 50 PSI)

A low-pressure switch protects your compressor by shutting the system down if refrigerant pressure drops too low (which usually means low charge or a restriction). If your AC shuts off and won’t restart for a while, the low-pressure switch may be tripping — or it may need replacement.

Specs: Opens at 50 PSI, closes at 90 PSI, 1/4″ SAE female flare fitting, automatic reset

Replaces: PLP5090, SLP5090

Fits: Universal — works with most residential and commercial HVAC and refrigeration systems

Need help? See our Furnace Short Cycling Guide.

In stock at Open To Public HVAC Parts in Dallas. We test parts at the counter before you buy. Call or text (214) 340-9421.

Specs

• TypeRefrigerant low-pressure cutout switch
• Open Pressure50 PSI
• Connector1/4" spade terminals
• ResetAutomatic (closes when pressure returns to normal)
• OEM CompatibilityUniversal

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• PLP5090
• SLP5090

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

Fits these models

• Universal refrigerant low-pressure cutout switch — protects compressors on residential split systems, heat pumps, and mini-splits from low-charge / restricted-suction conditions
• Fits any system whose data plate calls for the matching open-pressure spec (10/20/25/35/40/45/50 PSI)
• Verify your refrigerant type (R-22 / R-410A / R-32 / R-454B) — pressure cutout values are different per refrigerant

My low-pressure switch keeps tripping -- what's wrong?

Low-pressure trips almost always = low refrigerant charge (slow leak), restricted suction line (kink, clogged drier, frozen evaporator), or wrong superheat. Hook up gauges, verify charge AND superheat against the data plate. Just replacing the switch won't fix anything if the charge is low.

My high-pressure switch keeps tripping -- what's wrong?

High-pressure trips = dirty condenser coil (most common), failed condenser fan motor, overcharge, or non-condensables in the system. Clean the coil with a pressure washer, verify fan RPM, recover and weigh-in factory charge. Switch is usually fine.

What's the difference between open-at and close-at pressure?

A low-pressure switch with "OPEN @ 50 PSI" trips out (opens the safety circuit) when suction pressure falls to 50 PSI. The close-pressure is higher (system has to recover before restart). High-pressure works the opposite way -- opens at high pressure, closes when it drops back.

Can I replace a 50-PSI switch with a 40-PSI switch?

Yes, usually. Refrigerant pressure switches are interchangeable across brands and systems as long as the new switch is within 10-20% of the original pressure rating and has the same mechanical connection style. 40 PSI is 80% of 50 PSI (within 20%), so it'll work for most applications. If you're going further than that (e.g., a 40 PSI switch replacing a 60 PSI switch), verify against the system's design envelope.

What about connection style?

The mechanical connection has to match -- screw-on switches use a Schrader-style port; braze-in switches solder directly into the suction or discharge line. You can't swap between these two styles without changing the port fitting.

How do I test a refrigerant pressure switch?

Hook up gauges. With the system off (pressures equalized), the switch should read OPEN if pressure is in the trip range, CLOSED otherwise. Use a multimeter on the switch terminals for continuity. Bring it in and we'll bench-test free.