Service manual

41
Troubleshooting
Fault code 54, TACHO, NO SET SIGNAL
DLCU counts the tacho pulses from the motor in order to guarantee that
the drum is stationary when the door is opened. To ensure that the signal
from the tacho generator is working correctly, DLCU compares the tacho
signal to a default value from the CPU processor, which is due to the CPU
having activated the motor. The tacho signal should always correspond
to the default value and if the tacho signal is present without the default
value, a fault message will be generated to CPU.
The fault message is filtered in such a way that the drum must rotate and
stop twice without the ”should rotate” signal being present before a fault
message is sent to CPU.
The DLCU processor will reset itself when the fault has disappeared.
CPU reads the fault message when the program finishes and generates a
fault code, the fault message is ignored between these two occasions.
Reason:
The fault can be caused by cross talk in circuits in the CPU, or caused by
damaged components in the CPU.
Action:
If the fault returns after a reset, change the CPU.