AC Thermistor Repair Cost Guide
Below are the typical repair costs for different AC thermistor issues, based on our standard rate of $125/hour:
Outdoor Air Temperature Thermistor
Typical Cost Range: $175-$250
Includes approximately 1-1.5 hours of labor plus parts ($25-$50). This thermistor is usually easily accessible, making it a straightforward replacement.
Return Air Temperature Thermistor
Typical Cost Range: $200-$300
Includes 1.5-2 hours of labor plus parts ($35-$60). Located inside the air handler, this repair may require additional time for access and testing.
Discharge Air Temperature Thermistor
Typical Cost Range: $250-$375
Includes 2-2.5 hours of labor plus parts ($40-$75). This repair often requires more extensive system access and careful handling of refrigerant lines.
Coil Temperature Thermistor
Typical Cost Range: $225-$325
Includes 1.5-2 hours of labor plus parts ($35-$70). Access to the coil area and proper positioning of the new thermistor are crucial for this repair.
Note: These prices are estimates and may vary based on:
- System accessibility
- Brand and model of your AC unit
- Additional repairs needed
- Emergency service requirements
All repairs include:
- Diagnostic testing
- Professional installation
- System performance verification
- 90-day labor warranty
AC Thermistor Repair Procedures
Discharge Air Sensor (DAS) Thermistor
Common symptoms:Inconsistent cooling, system short cycling, or incorrect temperature readings
Repair steps:
- Power down the AC system completely
- Locate the DAS thermistor near the indoor evaporator coil
- Disconnect the electrical connections
- Remove the mounting hardware securing the thermistor
- Test the thermistor with a multimeter to confirm failure
- Install new thermistor in the same position
- Reconnect electrical connections
- Restore power and test system operation
Outdoor Air Sensor (OAS) Thermistor
Common symptoms:Poor temperature regulation, system not responding to outdoor temperature changes
Repair steps:
- Turn off power to the outdoor unit
- Remove the access panel on the outdoor unit
- Locate the OAS thermistor (typically mounted on the exterior)
- Disconnect wiring harness
- Remove thermistor from mounting bracket
- Install new thermistor ensuring proper positioning
- Reconnect wiring
- Replace access panel
- Restore power and verify operation
Coil Temperature Sensor Thermistor
Common symptoms:Frost buildup, improper defrost cycling, irregular cooling performance
Repair steps:
- Disconnect power to the system
- Access the evaporator coil section
- Locate the coil sensor (usually clipped to the coil)
- Carefully remove sensor from coil
- Disconnect electrical connections
- Install new sensor ensuring good contact with coil
- Secure sensor with clip or mounting hardware
- Reconnect wiring
- Close access panels
- Restore power and test operation
Return Air Sensor Thermistor
Common symptoms:Inaccurate temperature readings, improper cycling, comfort issues
Repair steps:
- Turn off system power
- Access the return air section
- Locate thermistor in return air stream
- Remove mounting hardware
- Disconnect electrical connections
- Install new thermistor in same location
- Secure mounting hardware
- Reconnect wiring
- Restore power and verify proper operation
Important Notes:
- Always use manufacturer-approved replacement parts
- Ensure proper electrical connections and mounting
- Verify correct resistance values with a multimeter when possible
- Consider professional service if unsure about any repair steps
Note: These procedures are general guidelines. Specific models may require different steps or specialized procedures. When in doubt, consult your AC system's manual or contact a certified HVAC technician.
Understanding AC Thermistors
An AC Thermistor (Temperature-dependent resistor) is a type of resistor whose resistance changes significantly with temperature. In air conditioning systems, thermistors play crucial roles in temperature sensing and system protection.
Types of AC Thermistors and Their Functions:
Discharge Pipe ThermistorLocated on the compressor's discharge pipe, this thermistor monitors refrigerant temperature as it exits the compressor. It protects the system from overheating by triggering a shutdown if temperatures become dangerously high.
Indoor Coil ThermistorPositioned on the indoor evaporator coil, this thermistor measures the coil's temperature to prevent freezing and ensure optimal heat exchange. It helps maintain efficient cooling operation and protects the system from frost buildup.
Outdoor Coil ThermistorMounted on the outdoor condenser coil, this thermistor monitors the condensing temperature. It helps regulate the outdoor fan speed and ensures proper heat rejection in cooling mode.
Return Air ThermistorLocated in the return air stream, this thermistor measures the temperature of air entering the indoor unit. It helps the system determine when to start and stop cooling cycles based on room temperature.
Supply Air ThermistorPositioned in the supply air stream, this thermistor monitors the temperature of air leaving the indoor unit. It helps ensure the system is providing proper cooling and can detect potential system issues.
Ambient Temperature ThermistorLocated outside the unit, this thermistor measures outdoor air temperature. It helps the system adjust its operation based on external conditions and ensures efficient performance across various weather conditions.
Note: The proper functioning of these thermistors is essential for your AC system's efficiency, performance, and longevity. Regular maintenance and timely replacement of faulty thermistors are recommended to maintain optimal system operation.
Common Failure Symptoms of AC Thermistor Malfunction
Common AC Thermistor Failure Signs and Maintenance Guide
Discharge Line Thermistor
Signs of Failure:
- Inconsistent or incorrect temperature readings
- AC system shutting down unexpectedly
- Error codes related to discharge temperature
- Compressor cycling on and off frequently
Service Schedule: Inspect annually during regular AC maintenance. Replace every 3-5 years or when showing signs of failure.
Outdoor Air Thermistor
Signs of Failure:
- System showing incorrect outdoor temperature readings
- Inefficient system operation
- Unusual cycling patterns
- Inconsistent cooling performance
Service Schedule: Check during bi-annual maintenance. Replace every 5-7 years or when malfunctioning.
Indoor Air Thermistor
Signs of Failure:
- Inaccurate indoor temperature readings
- System running longer than necessary
- Inconsistent room temperatures
- Thermostat displaying wrong temperature
Service Schedule: Inspect during regular maintenance (twice yearly). Replace every 5-7 years or when showing signs of malfunction.
Liquid Line Thermistor
Signs of Failure:
- Incorrect subcooling measurements
- Poor cooling performance
- System pressure issues
- Refrigerant flow problems
Service Schedule: Check during annual maintenance. Replace every 4-6 years or when failing.
Note: These are general guidelines. Actual service intervals may vary based on usage, environmental conditions, and manufacturer recommendations.
How It Works
- Get a quote online or set-up a time to have your vehicle looked at.
- Pick time slots that work for you, easily, online.
- We will confirm appointments and send reminders.
- Our mechanics bring everything that is needed to you.
- All you have to do is provided a safe area for the work to be performed.
What we need from you
- A safe place to work on your vehicle
- No working on the side of busy roads
- No working on unstable or steep surfaces.
- We do not perform repairs during severe weather.
- Authorization from a property owner or management.
- Repair work done in a parking lot or at your requires permission.
- We do not do repairs in areas restricted by law.
Common Questions
Service Area
Our primary service area is greater Grand Rapids and includes Comstock Park, East Grand Rapids, Grandville, Kentwood, Walker, and Wyoming
Our secondary service area is provided by our Belding location and includes: Belding, Greenville, Ionia and the sorrounding areas.
Contact us if you have any questions about where we provide services.
