Heat pumps · Error codes · York
bAYork · YKF Mono (CNC/CRC, 5-16 kW, R32)
bA on a York YKF Mono: T4 sensor out of operation range
Short answer
On a York heat pump, bA means: T4 sensor out of operation range. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: T4 sensor out of operation range.
Likely causes:
- Cause/corrective action column not provided in this YORK manual table; see Midea M-Thermal service documentation for the equivalent code (not copied here).
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
What you can check
- Read and note the exact code shown on the controller display.
- Check the heat pump's breaker/isolator at the consumer unit is on.
- Restart once via the controller (OFF then ON) as the manual allows; if the code returns, call an engineer.
What the engineer will check
- Cause/corrective action column not provided in this YORK manual table; see Midea M-Thermal service documentation for the equivalent code (not copied here).
Sources
- YKF Air Source Heat Pump System - Monoblock Single and Triphase, 5 kW to 16 kW - Installation, Commissioning, Operation and Maintenance, Form 201.55-ICOM1.EN.CE (622) ↗ · 201.55-ICOM1.EN.CE (622) · page PDF 61 (printed 58) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026