York Error Code R4: High Limit Switch Open

Severity
Warning
Type
digital display
Estimated repair cost: $75 — $200 (parts + labor)
Warning: Your York furnace has shut down due to a high limit error. This prevents overheating, but you'll need to troubleshoot to restore heat.

How to Fix York Code R4

  1. Step 1: Replace the air filter. A dirty air filter is the most common cause of overheating. Use the filter size noted on the furnace.
  2. Step 2: Ensure all return air vents are open and unobstructed. Do not block them with furniture or rugs.
  3. Step 3: Wait 30 minutes, then try resetting the furnace by turning it off and then on again at the breaker. If the error reappears, call a qualified HVAC technician.

How to Reset York Code R4

  1. Turn off the furnace power switch, usually located on or near the unit.
  2. Turn off the circuit breaker for the furnace. Wait 30 seconds.
  3. Restore power at the breaker and flip the furnace switch back on.
  4. Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does York Error Code R4 Mean?

The R4 error code on your York furnace indicates that the high limit switch has opened. This switch is a critical safety device designed to shut down the furnace if it gets too hot. Think of it like a circuit breaker for heat. When the furnace temperature exceeds a safe threshold, the high limit switch trips, cutting off the gas supply and blower motor. This prevents potential damage to the furnace components and, more importantly, protects your home from a fire hazard. The R4 code means the furnace control board detected that the switch is open (tripped). It's important to address the underlying cause of the overheating, not just reset the system.

Common Causes

  • Dirty air filter restricting airflow
  • Blocked return air vents reducing airflow to the furnace
  • Faulty blower motor or capacitor causing reduced airflow
  • Overfiring furnace due to a gas valve issue
  • Defective high limit switch tripping prematurely

Diagnostic Steps

If... Check Expected
Furnace is locked out with R4 error Measure resistance across the high limit switch terminals with the furnace off Should read near 0 ohms (closed circuit). Infinite resistance indicates an open switch.
High limit switch is open Inspect the physical condition of the heat exchanger for cracks or damage Heat exchanger should be intact with no visible signs of stress or corrosion.
Heat exchanger appears OK Measure the voltage to the blower motor Should match the voltage indicated on the motor nameplate (e.g., 120VAC).
Blower voltage is correct Measure the amperage draw of the blower motor Should be within the range specified on the motor nameplate. High or low amperage indicates a failing motor.

Applicable York Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
High Limit Switch 024-36375-000 — Find Part
Blower Motor Capacitor — — —
Air Filter — — —

Related Codes on Same Models

Other codes that affect the same York model families as R4.

Code Description Severity
A4 Improper Thermostat Wiring Warning
AF Low Flame Current Critical
R1 Flame Without Call Critical
R2 Pressure Switch Stuck Closed Warning
R3 Pressure Switch Stuck Open Warning
R5 Rollout Switch Open Critical
R6 Gas Valve Failure Critical
R7 Ignition Lockout Critical
R9 Reversed Polarity Critical