Index: firmware/App/Modes/ModeFill.c
===================================================================
diff -u -r8a4182663ef6b12e3fd6414c0c14158943cd4ce1 -rf656b17f3d8d93b4fca49c9725e096e7eb55acc7
--- firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision 8a4182663ef6b12e3fd6414c0c14158943cd4ce1)
+++ firmware/App/Modes/ModeFill.c	(.../ModeFill.c)	(revision f656b17f3d8d93b4fca49c9725e096e7eb55acc7)
@@ -123,8 +123,11 @@
     setPrimaryHeaterTargetTemperature( 39.0 );
     // TODO remove
 
-    startPrimaryHeater();
+    // NOTE: The target flow rate should be set prior to setting the start primary heater
+    // because the initial guess in the heaters driver needs the target flow to calculate
+    // the new PWMs for the main and small primary heaters
     setROPumpTargetFlowRate( TARGET_RO_FLOW_RATE_L, TARGET_RO_PRESSURE_PSI );
+    startPrimaryHeater();
 }
 
 /*********************************************************************//**