The 5D51-35 Fan & Limit Control (White-Rodgers / Copeland Comfort Control) is a combination temperature control designed to regulate blower fan operation and provide high-temperature safety protection in residential and light commercial furnaces. Featuring a 5-inch insertion element, this control automatically starts and stops the blower based on plenum temperature while also protecting the furnace from overheating through its integrated limit switch function.

Cross-Reference

• 5D51-35
• White-Rodgers 5D51-35
• Copeland Comfort Control 5D51-35
• 5D5135

Direct OEM

White-Rodgers 5D51-35

Compatible Brands

• White-Rodgers
• Emerson
• Copeland
• York
• Coleman
• Luxaire
• Goodman
• Rheem
• Universal Furnace Applications

Application

Used in warm air furnaces to:

• Control blower fan operation
• Prevent circulation of cold air during startup
• Maintain proper furnace temperature control
• Provide high-limit overheating protection
• Automatically cycle the blower during heating operation
• Protect heat exchangers from excessive temperatures

Related Components

• Fan & Limit Control
• High Limit Switch
• Fan Switch
• Furnace Control Board
• Blower Relay
• Blower Motor
• Transformer
• Thermostat
• Temperature Control Dial

Technician Notes

The 5D51-35 is a combination fan and limit control utilizing a 5-inch sensing element that extends into the furnace plenum. This design provides both blower control and high-temperature safety protection in a single assembly. Always verify insertion length, mounting dimensions, and temperature settings before replacement.

If the blower runs continuously, fails to start, or the furnace cycles on high limit, inspect airflow, blower operation, filter condition, and heat exchanger temperatures before condemning the control.

Common Symptoms of Failure

• Blower fan runs continuously
• Blower fails to start
• Furnace overheats
• High-limit shutdowns
• Short cycling
• Inconsistent blower operation
• Poor airflow during heating
• Excessive furnace temperatures
• No heat output

Installation Tips

1. Disconnect power before servicing.
2. Mark all wire locations before removal.
3. Verify the 5-inch insertion length matches the original control.
4. Secure the sensing element fully within the plenum.
5. Inspect wiring terminals for corrosion or overheating.
6. Check blower motor amperage and operation.
7. Verify fan and limit settings after installation.
8. Test the furnace through a complete heating cycle.

Recommended Inspection Items

• Blower motor condition
• Air filter restriction
• Heat exchanger temperature rise
• Fan relay operation
• Wiring terminals
• Furnace control board
• Supply and return airflow
• Venting system
• Blower wheel cleanliness