H06.79 on a Baxi HP60 / Baxi Assure HP55 High Temperature Monobloc ASHP: ODU flow temp err Flow temperature sensor is on error in the outdoor unit
Short answer
On a Baxi heat pump, H06.79 means: ODU flow temp err Flow temperature sensor is on error in the outdoor unit. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: ODU flow temp err Flow temperature sensor is on error in the outdoor unit.
Part involved: temperature sensor.
Likely causes:
- The connector for sensor Tw_out is loose. Reconnect it. The connector for sensor Tw2 is loose. Reconnect it. The connector for sensor Tw2 is wet or contains water. Drain the water and dry the connector. Add a waterproof adhesive. sensor Tw2 is faulty. Replace it with a new sensor.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - system restarts automatically when the cause disappears (may run in degraded/back-up mode meanwhile).
Manual reset: not required once cause removed.
What you can check
- Note the exact code shown on the controller and when it appeared.
- The manual's user steps allow switching the system off and on once to see if the error clears; if the code returns, contact the installer.
- If the code persists or returns, contact a heat pump engineer.
What the engineer will check
- The connector for sensor Tw_out is loose. Reconnect it. The connector for sensor Tw2 is loose. Reconnect it. The connector for sensor Tw2 is wet or contains water. Drain the water and dry the connector. Add a waterproof adhesive. sensor Tw2 is faulty. Replace it with a new sensor.
Who to ask for: heat pump engineer (controls / sensors).
Certification: Manufacturer-trained heat pump engineer.
What you might notice
Sources
- Installation, user and service manual - Indoor unit ASHP Control ↗ · 7887625 - v04 - 22072025 · page 133 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026