Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r3fc87449b1c5b892a7f86430b7b8c49190ae56a8 -r7d4711edd7b40cd3e29f43e766f79a8a09586fe9
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 3fc87449b1c5b892a7f86430b7b8c49190ae56a8)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 7d4711edd7b40cd3e29f43e766f79a8a09586fe9)
@@ -1,14 +1,14 @@
 /**************************************************************************
 *
-* Copyright (c) 2019-2023 Diality Inc. - All Rights Reserved.
+* Copyright (c) 2019-2024 Diality Inc. - All Rights Reserved.
 *
 * THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
 * WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
 *
 * @file    SystemComm.c
 *
-* @author  (last)      Michael Garthwaite
-* @date    (last)      05-Sep-2023
+* @author  (last)      Sean Nash
+* @date    (last)      05-Oct-2023
 *
 * @author  (original)  Dara Navaei
 * @date    (original)  05-Nov-2019
@@ -21,14 +21,15 @@
 #include "sci.h"
 #include "sys_dma.h"
 
-#include "DrainPump.h"
-#include "SystemComm.h"
 #include "Comm.h"
+#include "DrainPump.h"
+#include "Heaters.h"
 #include "Interrupts.h"
 #include "OperationModes.h"
+#include "SystemComm.h"
+#include "SystemCommMessages.h"
 #include "Timers.h"
 #include "Utilities.h"
-#include "SystemCommMessages.h"
 
 /**
  *  @addtogroup SystemComm
@@ -672,7 +673,8 @@
     if ( TRUE == didTimeout( timeOfLastHDCheckIn, HD_COMM_TIMEOUT_IN_MS ) )
     {
         hdCommunicationStatus.data = FALSE;
-        setHDOperationMode( 0, 0 );   // If HD off or not connected, consider HD mode is fault.
+        setHDOperationMode( 0, 0 );      // If HD off or not connected, consider HD mode is fault.
+        stopHeater( DG_TRIMMER_HEATER ); // If HD off or not connected, ensure trimmer heater is off.
     }
 }