Fault Diagnosis and Maintenance of Siemens Washing Machine Electric Program Controller
The electric program controller is a contact switch, its structure consists of contacts and spring (pressure) sheets. The metal contacts are riveted on the spring sheets, which are connected to the control circuit; the spring sheet relies on its own elasticity and external force to make the contacts touch or separate, thereby controlling the circuit's connection and disconnection. Common faults are as follows:
(1) Serious burn damage on the contact surface, increased contact resistance. For example, during the instant of connection and disconnection, if the sparks are very large, the contact surface should be checked in time for any burn damage. If the damage is serious, it can be smoothed and leveled with a small file, or polished with fine sandpaper. If the contact surface appears smoke-stained and burnt, it indicates carbon accumulation on the surface. First, clean it with anhydrous alcohol or carbon tetrachloride, then polish it clean with sandpaper.
(2) Contact adhesion. This occurs due to severe burn damage on the contacts, resulting in excessive contact resistance. In this case, first identify which side of the contact switch is the normally closed end and which side is the normally open end, then carefully separate the contacts and repair and polish them.
(3) After long-term operation, the spring sheet reduces in elasticity and undergoes deformation. At this point, mechanical methods are often used for restoration. If normal function cannot be restored after repair, consider replacing the program controller. Note that after repair, the contacts should have a certain amount of contact force when they touch.
(4) Spring sheet twisting and deformation. This type of fault is relatively rare and can only be repaired by mechanical means. After repair, ensure that it does not cause confusion in the contact switch's on/off state.
(5) Contacts turn black due to corrosion, although they have made contact but do not conduct electricity. The blackened contacts can be polished with sandpaper until they shine and reveal the metal surface, allowing the two contacts to conduct electricity normally. The spring sheets of the contact switches are mostly fixed in plastic parts by injection molding and cannot be disassembled and replaced. When the contacts are damaged beyond repair, or the spring sheet, cam breaks, or the plastic bracket deforms making replacement difficult, the entire program controller must be replaced.
Released by the Beijing Siemens Washing Machine After-sales Service Center on September 23, 2011.