**Mitsubishi Air Conditioner, FS and DS Control Panel Button Failure**
**Fault Phenomenon:** The control panel buttons are unresponsive, but the remote control can still operate.
**Cause Analysis:** Since the remote control operation is functioning properly, it can be ruled out that the issue is with the main computer board. Upon investigation, it was found that the diodes D1~D12 used for button scanning on the display board produced by Changzhou Hongdu were low-frequency diodes (IN4007). However, the main program processes button signals at a high frequency. This mismatch causes some control panels to be incompatible with their respective motherboards, preventing the main program from correctly responding to button signals, leading to button failure. This incompatibility between the control panel and motherboard mainly occurs in products manufactured by Changzhou Hongdu Electronics Co., Ltd. before February 2004.
**Solution Measures:** When such a fault is detected, the control panel can be replaced with one produced by Changzhou Hongdu Electronics Co., Ltd. after February 2004 or with a compatible control panel from another company. Alternatively, the diodes D1~D12 on the control panel can be replaced with high-frequency diodes IN4148.
**Experience Summary:** In addition to DS button failures, the temperature adjustment button on the FS (Y) model may also fail. During the design of the display panel, insufficient consideration was given to the tactile feedback of the buttons, resulting in small gaps. Deformation of the plastic button panels produced by the plastic division and insufficient spacing between the middle panel can cause operational failures. For this type of fault, simply replacing the same model control panel will resolve the issue.
**Source Article:** [http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3760866](http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3760866)