Carrier HH19ZA940 Limit Switch
The Carrier HH19ZA940 Limit Switch is a critical OEM safety component engineered for precise thermal regulation within Carrier fan coil units, packaged systems, and secondary heating assemblies. This 85-140 degree limit switch operates as a normally closed (NC) safety, opening the circuit when the sensed temperature exceeds 140°F to prevent heat exchanger or coil damage. Once the system cools back to 85°F, the automatic reset limit switch closes the contacts, restoring operation without requiring manual intervention from the end-user.
Designed for heavy-duty HVACR applications, this Carrier replacement limit switch features a robust snap-action mechanism and SPDT contact arrangement, ensuring rapid and definitive switching. It is rated for 20A at 120VAC and 15A at 240VAC, making it a versatile choice for a variety of HVAC high limit control needs. Pro-tip for technicians: always verify the specific temperature stamped on the existing bracket, as the HH19ZA940 is specifically tuned for systems requiring this exact 55-degree differential to maintain safe airflow cycles.
Key Benefits- OEM Compatibility: Precision-manufactured to match original Carrier factory specifications for reliable fit and function in 40YR and similar series units.
- Automatic Reset Functionality: Eliminates nuisance service calls by automatically restoring power once temperatures reach safe operating levels.
- High Electrical Rating: Capable of handling significant inductive loads, suitable for both residential and commercial air handlers.
- Compact Snap-Action Design: Facilitates easy installation in tight furnace or fan coil compartments while providing precise temperature sensing.
What causes a Carrier HH19ZA940 to trip?
While the switch itself may reach its end-of-life, frequent tripping is typically a symptom of restricted airflow, such as a clogged filter, a failing blower motor, or dirty evaporator coils causing the internal temperature to exceed the 140°F threshold.
Can I test this switch with a multimeter?
Yes. For a standard continuity test, disconnect the wires and check the terminals. At room temperature, the switch should show continuity (0 ohms). If it remains open at room temperature, the internal disc has failed and requires replacement.
Is this switch compatible with other brands?
While primarily designed for Carrier, Bryant, and Payne equipment, this switch can be used in any application requiring an 85-140°F broad-range automatic reset, provided the physical mounting footprint and electrical ratings align.
This item is not eligible for free shipping.
Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.
QUESTIONS & ANSWERS
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In my old home, I had a Janitrol split system A/C. Once in a while the fan would not kick in and the compressor would run, causing it to freeze. I replaced the sequencer / limit switch, and it worked fine. I moved, and my A/C is a Carrier. Same problem just came up, every so often the fan will not engage, so I want to buy Carrier Limit Switch HH19ZA940, do you think this would be the same fix? Thank you.
Unfortunately there are numerous parts that may cause the same problem so it is hard to pinpoint what the problem is without checking it out in the field. Sorry we are not sure if this is the part that is causing the problem.