Hisense air conditioner, maintenance experience summary; air conditioner not cooling, communication fault 9Z.

**Haier Air Conditioner: No Cooling, Communication Failure**

**Fault Phenomenon:** The indoor unit's operation light flashes (all other lights are off), and neither the indoor nor outdoor units work.

**Cause Analysis:** Based on user feedback, the machine operates normally upon startup without any of the issues reported by the user. However, after about 30 minutes, both the indoor and outdoor units stop working, with the control panel's operation light flashing. Pressing any button results in no response from the air conditioner. After unplugging the power and restarting the machine, it works normally again, but the same fault reoccurs after another 30 minutes. Since the air conditioner was cooling properly before it stopped, there should be no problem with the system itself. Therefore, it is preliminarily judged to be an external signal issue. This can also be confirmed by the fault display codes provided by the company as a communication failure. Upon inspection, the signal connection line between the indoor and outdoor units is found to be normal, so the issue is likely due to external signal interference.

**Repair Measures:** A 103 ceramic capacitor can be connected in parallel on the computer board's signal line, or the interference-resistant C3Y computer board produced by Huafa can be replaced, which eliminates the fault.

**Experience Summary:** When repairing, it is important to carefully observe the indicator status on the panel during the fault occurrence. According to the fault codes provided by the company, faults can be quickly identified. If there is a fault with the outdoor pipe temperature sensor or a break in the signal connection line between the indoor and outdoor units, the timer indicator light will flash at a rate of once per second if there is no digital display function. If there is a digital display function, the E2 code will be displayed. For the three-phase A series, the temperature light will flash while all other indicator lights remain off.

**Source of Article:** http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3489688.