Installation Manual

Electrical & Electronic Application And Installation Manual
Production Release Version 1.0
Page 219
16.3.2 System Purge
16.3.2.1 DEF System Purge Operation
Note: The System DEF must be purged of DEF on engine shutdown to
protect the system components from damage due to DEF freezing. For
this reason it is important that electrical power is maintained to the
engine ECM and aftertreatment system after the ignition has been turned
off. It is therefore important that the machine battery disconnect switch
is not operated until the system purge has been completed.
To ensure that all DEF is removed from the system prior to system shutdown
(requested by the removal of the ignition signal to the ECM) a DEF purge
sequence is activated. This purge procedure operates during every engine
shutdown sequence post termination of the delayed engine shutdown (if
used). The purge process ensures that any risks associated with the thermal
expansion and contraction of freezing DEF are minimized.
The purge process is conducted by maintaining electrical power to the DEF
pump post engine shutdown. To allow the purge sequence to complete,
electrical power must be maintained to the DEF dosing system and to the un-
switched battery connections at the engine ECM J1 connector. Engine
ignition signal is not required as the purge process operates post the engine
ignition OFF signal.
To prevent the purge cycle being disabled by the removal of power to the
system by the use of a battery disconnect switch, Perkins mandate that a
“Wait To Disconnect” lamp is connected locally to the battery disconnect
switch. The Wait to Disconnect lamp operates as shown below and will
remain illuminated whilst there is electrical power to the DEF system. Once
the lamp turns OFF purge is complete and it is safe to use the battery isolator
switch.
Fig 16.9 System Purge Without Delayed Engine Shutdown 1204F & 1206F