Condenser coil temperature sensor fault for Circuit A. The T3-A sensor fault can be due to a faulty sensor that is shorted / open, or harness failure.  

1.Locating the T3-A sensor

Locate the sensor to begin diagnostics. The sensor is located in the compressor cabinet pictured below in Figure 1. Unplug sensor and measure the ohms and make sure it match's the chart in Figure 4. If the sensor is reading correctly, connect the sensor to the harness again. 

If the sensor is not measuring correctly, is shorted, or grounded replace the sensor. 

Figure 1

2. Locate the T3-A Plug connector on the Main Board CN22

Look at the wiring schematic located on the control box cover for the sensor and plug information. Once the information is located you will need to find the plug on the main board. See Figure 2 and Figure 3 for CN22 plug location on the board. Unplug the connector and again ohm it and see if it also measures the same as the sensor did in step one. It the sensor measures correctly plug it back onto the board. If it does not measure correctly, is shorted or grounded replace harness. 

Figure 2

Figure 3

3. Verifying sensor voltage

Unplug CN22 and measure DC voltage on the board plug socket pins. Voltage should read 4.99-5 VDC. If no voltage is present, verify Main board has the correct line voltage CN3 and CN16 has 24vac. If voltage is present to the board but not at CN22, replace the Main Board.  

4.Temperature Sensor Calibration Chart 

Measure the OHMs on the sensor and the temperature at the sensor with a temperature probe and compare them to the chart below to verify calibration is correct. 

Figure 4

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.