York S1-3500-3121 Limit Switch
When you are troubleshooting a mid-efficiency or high-efficiency furnace that is short-cycling or displaying a four-flash diagnostic code, the York S1-3500-3121 Limit Switch is the OEM replacement part required to restore safe operation. This is a normally closed (NC) safety device calibrated for an opening temperature of 165°F and a closing temperature of 105°F. As a genuine Johnson Controls component, it is designed for drop-in compatibility with York, Coleman, and Luxaire gas furnaces. The automatic reset functionality ensures the control circuit re-engages only after the plenum has cooled by 60 degrees, protecting the heat exchanger from thermal fatigue and preventing high-limit lockout. For a reliable install, this switch features standard 1/4-inch spade terminals and a rigid mounting bracket designed to withstand high-vibration environments. Before swapping the part, always verify your static pressure and inspect the blower wheel; a tripped S1-3500-3121 is frequently a symptom of restricted airflow across the evaporator coil or a clogged filter rather than a standalone component failure.
Key Benefits for Contractors
- Factory Calibrated: Ensures precise 165°F trip points to maintain equipment UL certifications and safety standards.
- Automatic Reset Logic: High-performance thermal disc resets at 105°F, reducing nuisance service calls after minor airflow interruptions.
- OEM Construction: High-grade materials designed for York HVAC gas furnaces, offering superior thermal response compared to generic alternatives.
- Direct Fitment: Standardized mounting footprint and terminal spacing allow for rapid field replacement on TG9S and GY9S models.
- Circuit Protection: Engineered to handle 24VAC systems, acting as the primary safety sentinel against plenum overheating.
Common Questions
What is the most common cause of a tripped 165°F limit switch?
In most York furnaces, this switch trips due to inadequate airflow. You should immediately inspect for a dirty air filter, closed supply registers, or a blower motor that isn't ramping up to the correct CFM. If the switch trips instantly upon ignition, check for a cracked heat exchanger or restricted secondary cell.
How do I verify if the S1-3500-3121 is defective?
With the furnace power off and the part cooled to room temperature, use a multimeter to test for continuity. A functioning switch will show a closed circuit (0 ohms). If the meter shows infinite resistance (OL) at room temperature, the internal bimetal disc is likely warped or stuck in the open position and requires immediate replacement.
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.
York S1-3500-3121 Limit Switch
When you are troubleshooting a mid-efficiency or high-efficiency furnace that is short-cycling or displaying a four-flash diagnostic code, the York S1-3500-3121 Limit Switch is the OEM replacement part required to restore safe operation. This is a normally closed (NC) safety device calibrated for an opening temperature of 165°F and a closing temperature of 105°F. As a genuine Johnson Controls component, it is designed for drop-in compatibility with York, Coleman, and Luxaire gas furnaces. The automatic reset functionality ensures the control circuit re-engages only after the plenum has cooled by 60 degrees, protecting the heat exchanger from thermal fatigue and preventing high-limit lockout. For a reliable install, this switch features standard 1/4-inch spade terminals and a rigid mounting bracket designed to withstand high-vibration environments. Before swapping the part, always verify your static pressure and inspect the blower wheel; a tripped S1-3500-3121 is frequently a symptom of restricted airflow across the evaporator coil or a clogged filter rather than a standalone component failure.
Key Benefits for Contractors
- Factory Calibrated: Ensures precise 165°F trip points to maintain equipment UL certifications and safety standards.
- Automatic Reset Logic: High-performance thermal disc resets at 105°F, reducing nuisance service calls after minor airflow interruptions.
- OEM Construction: High-grade materials designed for York HVAC gas furnaces, offering superior thermal response compared to generic alternatives.
- Direct Fitment: Standardized mounting footprint and terminal spacing allow for rapid field replacement on TG9S and GY9S models.
- Circuit Protection: Engineered to handle 24VAC systems, acting as the primary safety sentinel against plenum overheating.
Common Questions
What is the most common cause of a tripped 165°F limit switch?
In most York furnaces, this switch trips due to inadequate airflow. You should immediately inspect for a dirty air filter, closed supply registers, or a blower motor that isn't ramping up to the correct CFM. If the switch trips instantly upon ignition, check for a cracked heat exchanger or restricted secondary cell.
How do I verify if the S1-3500-3121 is defective?
With the furnace power off and the part cooled to room temperature, use a multimeter to test for continuity. A functioning switch will show a closed circuit (0 ohms). If the meter shows infinite resistance (OL) at room temperature, the internal bimetal disc is likely warped or stuck in the open position and requires immediate replacement.
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.
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
When you are troubleshooting a mid-efficiency or high-efficiency furnace that is short-cycling or displaying a four-flash diagnostic code, the York S1-3500-3121 Limit Switch is the OEM replacement part required to restore safe operation. This is a normally closed (NC) safety device calibrated for an opening temperature of 165°F and a closing temperature of 105°F. As a genuine Johnson Controls component, it is designed for drop-in compatibility with York, Coleman, and Luxaire gas furnaces. The automatic reset functionality ensures the control circuit re-engages only after the plenum has cooled by 60 degrees, protecting the heat exchanger from thermal fatigue and preventing high-limit lockout. For a reliable install, this switch features standard 1/4-inch spade terminals and a rigid mounting bracket designed to withstand high-vibration environments. Before swapping the part, always verify your static pressure and inspect the blower wheel; a tripped S1-3500-3121 is frequently a symptom of restricted airflow across the evaporator coil or a clogged filter rather than a standalone component failure.
Key Benefits for Contractors
- Factory Calibrated: Ensures precise 165°F trip points to maintain equipment UL certifications and safety standards.
- Automatic Reset Logic: High-performance thermal disc resets at 105°F, reducing nuisance service calls after minor airflow interruptions.
- OEM Construction: High-grade materials designed for York HVAC gas furnaces, offering superior thermal response compared to generic alternatives.
- Direct Fitment: Standardized mounting footprint and terminal spacing allow for rapid field replacement on TG9S and GY9S models.
- Circuit Protection: Engineered to handle 24VAC systems, acting as the primary safety sentinel against plenum overheating.
Common Questions
What is the most common cause of a tripped 165°F limit switch?
In most York furnaces, this switch trips due to inadequate airflow. You should immediately inspect for a dirty air filter, closed supply registers, or a blower motor that isn't ramping up to the correct CFM. If the switch trips instantly upon ignition, check for a cracked heat exchanger or restricted secondary cell.
How do I verify if the S1-3500-3121 is defective?
With the furnace power off and the part cooled to room temperature, use a multimeter to test for continuity. A functioning switch will show a closed circuit (0 ohms). If the meter shows infinite resistance (OL) at room temperature, the internal bimetal disc is likely warped or stuck in the open position and requires immediate replacement.
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.
