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Error code reference

Frigidaire Air Conditioner Error Code CS

Condenser thermostat sensor has failed (heat pump models only); displays for 1 second every 10 seconds.

Frigidaire codesFrigidaire air conditioner codes

Condenser thermostat sensor has failed (heat pump models only); displays for 1 second every 10 seconds.

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What CS means on a Frigidaire air conditioner

The CS error code on Frigidaire heat pump models indicates a failure in the condenser thermostat sensor. This sensor is a thermistor-based component mounted on the condenser coil assembly that monitors refrigerant-side temperatures during heating and cooling cycles. The control board uses this data to regulate compressor operation, protect against overcooling or overheating of the condenser, and manage defrost cycling in heat pump mode. When the board detects that the sensor's signal is outside of its expected range, it triggers the CS fault.

The distinctive display behavior, showing the code for 1 second out of every 10 seconds, is a pulsed alert pattern. This is designed to draw attention without completely interrupting the unit's status display. It does not necessarily mean the unit has shut down entirely, but the control system is operating with compromised or missing temperature feedback from the condenser side.

Common failure modes include an open or shorted thermistor, damaged wiring between the sensor and the control board, or a corroded connector at either end of the sensor harness. Because this code applies exclusively to heat pump models, technicians should focus diagnostics on the condenser thermostat sensor circuit specific to heat pump wiring configurations rather than standard cooling-only sensor paths.

Source: manufacturer service documentation.

Common causes of CS

  1. 01

    Failed condenser thermistor

    Part replacement

    The thermistor itself may have developed an open or short circuit, causing it to send a signal outside the acceptable range to the control board. Resistance testing of the sensor at the connector will reveal whether it has failed.

  2. 02

    Damaged sensor wiring harness

    Part replacement

    The wiring between the condenser thermostat sensor and the control board can become pinched, cut, or chafed over time, especially near sharp metal edges on the cabinet. Visually inspect the full wire run and check for continuity.

  3. 03

    Corroded or loose connector

    Wiring / connection

    Moisture intrusion at the sensor harness connector can cause corrosion on the terminals, leading to an intermittent or lost signal. Inspect both the sensor-side and board-side connectors for green or white oxidation and ensure a secure fit.

  4. 04

    Control board fault

    Part replacement

    If the sensor and all wiring test within spec, the control board's sensor input circuit may have failed. This is less common but should be considered after ruling out the sensor and wiring.

See the test procedure for each cause

Frequently asked questions about CS

What does CS mean on a Frigidaire air_conditioner?
The CS code on a Frigidaire heat pump air conditioner means the condenser thermostat sensor has failed or is sending an out-of-range signal. This code only appears on heat pump models and is displayed for 1 second every 10 seconds as a pulsed alert. The condenser thermostat sensor monitors temperatures at the condenser coil and is critical for safe and efficient heat pump operation.
Can I fix the CS error code myself?
Some causes of the CS code, such as a loose or corroded connector, can be addressed by a knowledgeable DIYer who is comfortable working inside an air conditioning unit. However, testing the thermistor and replacing components inside a heat pump system typically requires electrical diagnostic skills and knowledge of refrigerant-side components. If you are not experienced with HVAC diagnostics, a qualified technician is recommended.
Is it safe to keep running my Frigidaire heat pump with a CS error?
Operating the unit with a CS fault means the control board is missing accurate temperature feedback from the condenser sensor. This can reduce the system's ability to protect itself from overheating or over-cooling conditions during heat pump operation. Continued use without addressing the fault is not recommended, as it could cause additional stress on the compressor or other components.
How much does it cost to repair a CS error on a Frigidaire heat pump?
Repair costs depend on the root cause. A condenser thermostat sensor replacement is generally an affordable part, with the sensor itself typically ranging from $15 to $60 depending on the model. If a service technician is needed for diagnosis and replacement, total repair costs including labor could range from $100 to $300. A control board replacement, if required, would be at the higher end of the cost range.
Will resetting the unit clear the CS error code?
A power reset may temporarily clear the CS code from the display, but if the condenser thermostat sensor or its wiring is actually faulty, the error will return once the control board re-evaluates the sensor signal. Resetting is useful as a first step to rule out a transient glitch, but a persistent CS code after reset indicates a real hardware issue that requires inspection and repair.

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