ACiQ mini split error code Fd
Refrigerant leak sensor communication fault. Also shown as FD.
- TypeProtection
- SystemRefrigerant circuit
- Can I fix it?Homeowner checks, then maybe a tech
- Applies toK-series (ACiQ-K09W-HP…, TCL-built)
What Fd means on a ACiQ
The board lost contact with the refrigerant leak sensor.
On this platform, Fd is a protection: the system stopped or throttled itself to prevent damage; many clear on their own once conditions return to normal.
Common causes
- A loose sensor connector.
- A failed sensor.
How to fix it yourself
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
- Reseat the leak sensor connector on the indoor board.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
A technician can replace the sensor.
Which ACiQ units show Fd
This page applies to ACiQ Standard single-zone (ACiQ-09Z-HP…B / W-HP) and multi-zone and K-series (ACiQ-K09W-HP…, SZDM / WHP / KZHP) units on the K-series (ACiQ-K09W-HP…, TCL-built). ACiQ's own documentation lists Fd as "Refrigerant leak sensor communication fault", the same definition used across the TCL platform it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where ACiQ shows this code
K-series (ACiQ-K09W-HP…, TCL-built): The indoor display shows the code in place of the set temperature. E codes are faults: something has failed and needs diagnosis. P, H, d and F codes are protections: the system stopped or throttled itself to prevent damage, and many clear on their own once conditions return to normal.
Other ACiQ codes
Same part of the system as Fd:
Fd on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Zone Air Fd Refrigerant leak sensor communication fault
Questions people ask
Can I reset a ACiQ Fd code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If Fd comes back, the fault is real and needs the checks above.
Is it safe to keep running a ACiQ showing Fd?
Not repeatedly. A protection code means the unit stopped itself to prevent damage, and resetting it over and over can turn a cheap repair into a compressor failure. Reset once, check the basics, and stop if it returns.
Do I need a technician for ACiQ Fd?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. A technician can replace the sensor.
Sources
- ACiQ Standard Single-Zone Mini Split Service Manual (SZ-Z-HP / W-HP), Quick Maintenance by Error Code
- ACiQ Mini-Split Air Handler and Condenser Service Manual (MS-SZDM / WHP / KZHP), error code table
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.