There are two different heat exchanger gas temperature errors on the V series Fujitsu VRF outdoor units. Thermistor TH7 is what measures this. So you can use service tools history and look to see what happened on TH7 (inlet into condenser) to make this happen.

Error: EA6.3

This is heat exchanger (COIL) gas temperature is abnormal in heat exchanger or coil 1. Basically , the temperature was either way too or way too low. 

Things to look out for:

• TH7 sensor not on pipe correctly
• TH7 Sensor is defective
• 4-way valve defective
• EEV1 defective
• Main PCB defective

Error: EA6.4

This is heat exchanger (COIL) gas temperature is abnormal in heat exchanger or coil 2. Basically , the temperature was either way too or way too low. 

Things to look out for:

• TH8 sensor not on pipe correctly
• TH8 Sensor is defective
• 4-way valve defective
• EEV2 defective
• Main PCB defective

In either case, you will have to perform the F3-40 code and then cycle power. Unit is locked out until this happens. After watch the unit run on service tool and send in the run data to us.