Rheem R802VA07542117MSA Error Code T085_F: Suction Line Temp Thermistor Failure
What Does Code T085_F Mean?
Fault code T085_F on the Rheem R802VA is a troubleshooting-level fault for two-stage models only. It indicates that the suction line temperature thermistor — a sensor used by the Electronic Expansion Valve (EXV) system for refrigerant superheat control — has failed or is reading outside the valid range.
The EXV (Electronic Expansion Valve) system is part of the cooling side of the HVAC system and controls refrigerant flow through the air conditioning coil. The suction line thermistor measures the temperature of refrigerant returning to the compressor; this data, combined with the suction pressure reading, allows the EXV controller to compute superheat and adjust the valve accordingly for efficient cooling operation.
Because this sensor relates to the cooling system rather than the heating combustion system, furnace heating should continue to operate normally with this fault code active. However, cooling performance may be degraded or the EXV may default to a fixed position without accurate superheat data. The T prefix indicates an intermittent condition.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed suction line temperature thermistor | Most common | ✗ Call a pro → |
| Disconnected thermistor wiring at control board | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Schedule a service call — the suction line thermistor should be tested and replaced by a qualified HVAC technician with refrigeration certification
- A technician should also check the thermistor wire connections at the EXV controller and the IFC board
- This fault only applies to two-stage R802VA models connected to a compatible cooling system with an EXV
✓ Verified against manufacturer service manual — March 2026