1. The self-priming function of the center door locking block is controlled by the electric circuit, and a fault in the electric circuit may cause the self-priming function to fail.
2, the center door locking block is subjected to long-term use and wear and tear, may also fail.
3, the airtightness between the door and the door frame is not good, which may lead to the center door locking block can not self-priming.