Tosot mini split error code U8
Indoor fan (PG motor) zero-crossing detection error.
- TypeFault
- SystemFan motor
- Can I fix it?Homeowner checks, then maybe a tech
What U8 means on a Tosot
On units with a PG-type indoor fan motor, the board lost the zero-crossing signal it uses to control the motor.
On this platform, U8 is a fault: something has failed or is disconnected and needs diagnosis.
Common causes
- A loose fan motor plug.
- A failed fan motor or its feedback circuit.
- A failed indoor board.
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 fan motor plug on the indoor board.
- Check that the blower wheel spins freely.
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
If the motor tests fine, the indoor board is the suspect.
Which Tosot units show U8
This page applies to Tosot Tosot single-zone and Tosot multi-zone units. Tosot's own documentation lists U8 as "Indoor fan (PG motor) zero-crossing detection error", the same definition used across the Gree 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 Tosot shows this code
The code shows on the indoor unit's display in place of the temperature. If the display is off, press the Light button on the remote. Some models also count out the code as indicator blinks. E codes are system protections and faults, F codes are mostly sensor faults, H codes are outdoor and compressor protections, U codes are motor and valve faults, and P codes are power-supply faults.
Other Tosot codes
Same part of the system as U8:
U8 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Blueridge U8 Indoor fan (PG motor) zero-crossing detection error
- Mitsubishi Electric U8 Outdoor fan motor fault
Questions people ask
Can I reset a Tosot U8 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If U8 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Tosot showing U8?
The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.
Do I need a technician for Tosot U8?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. If the motor tests fine, the indoor board is the suspect.
Sources
- Tosot owner's manual (error code table)
- Gree residential split service manuals
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.