diff --git a/secop_psi/ips_mercury.py b/secop_psi/ips_mercury.py
index f74972a..4c14ccf 100644
--- a/secop_psi/ips_mercury.py
+++ b/secop_psi/ips_mercury.py
@@ -26,6 +26,7 @@ from secop.lib.enum import Enum
 from secop.errors import BadValueError, HardwareError
 from secop_psi.magfield import Magfield
 from secop_psi.mercury import MercuryChannel, off_on, Mapped
+from secop.lib.statemachine import Retry
 
 Action = Enum(hold=0, run_to_set=1, run_to_zero=2, clamped=3)
 hold_rtoz_rtos_clmp = Mapped(HOLD=Action.hold, RTOS=Action.run_to_set,
@@ -52,7 +53,6 @@ class Field(MercuryChannel, Magfield):
     nslaves = 3
     slave_currents = None
     __init = True
-    __reset_switch_time = False
 
     def doPoll(self):
         super().doPoll()
@@ -98,15 +98,10 @@ class Field(MercuryChannel, Magfield):
     def read_switch_heater(self):
         value = self.query('PSU:SIG:SWHT', off_on)
         now = time.time()
-        switch_time = self.switch_time[self.switch_heater]
         if value != self.switch_heater:
-            self.__reset_switch_time = True
-            if now < (switch_time or 0) + 10:
+            if now < (self.switch_time[self.switch_heater] or 0) + 10:
                 # probably switch heater was changed, but IPS reply is not yet updated
                 return self.switch_heater
-        elif self.__reset_switch_time:
-            self.__reset_switch_time = False
-            self.switch_time = [None, None]
         return value
 
     def write_switch_heater(self, value):
@@ -155,16 +150,22 @@ class Field(MercuryChannel, Magfield):
         try:
             self.set_and_go(self.persistent_field)
         except (HardwareError, AssertionError):
-            state.switch_undef = self.switch_on_time or state.now
+            state.switch_undef = self.switch_time[self.switch_heater.on] or state.now
             return self.wait_for_switch
         return self.ramp_to_field
 
+    def ramp_to_field(self, state):
+        if self.action != 'run_to_set':
+            self.status = Status.PREPARING, 'restart ramp to field'
+            return self.start_ramp_to_field
+        return super().ramp_to_field(state)
+
     def wait_for_switch(self, state):
-        if self.now - self.switch_undef < self.wait_switch_on:
+        if state.now - state.switch_undef < self.wait_switch_on:
             return Retry()
         self.set_and_go(self.persistent_field)
         return self.ramp_to_field
-        
+
     def start_ramp_to_target(self, state):
         self.set_and_go(self.target)
         return self.ramp_to_target
diff --git a/secop_psi/magfield.py b/secop_psi/magfield.py
index ef90bc2..b7d42f6 100644
--- a/secop_psi/magfield.py
+++ b/secop_psi/magfield.py
@@ -76,33 +76,23 @@ class Magfield(HasLimits, Drivable):
     #     ArrayOf(TupleOf(FloatRange(unit='$'), FloatRange(unit='$/min'))), readonly=False)
     # TODO: the following parameters should be changed into properties after tests
     wait_switch_on = Parameter(
-        'wait time to ensure switch is on', FloatRange(0, unit='s'), readonly=False, default=61)
+        'wait time to ensure switch is on', FloatRange(0, unit='s'), readonly=False, default=60)
     wait_switch_off = Parameter(
-        'wait time to ensure switch is off', FloatRange(0, unit='s'), readonly=False, default=61)
+        'wait time to ensure switch is off', FloatRange(0, unit='s'), readonly=False, default=60)
     wait_stable_leads = Parameter(
         'wait time to ensure current is stable', FloatRange(0, unit='s'), readonly=False, default=6)
     wait_stable_field = Parameter(
-        'wait time to ensure field is stable', FloatRange(0, unit='s'), readonly=False, default=31)
+        'wait time to ensure field is stable', FloatRange(0, unit='s'), readonly=False, default=30)
     persistent_limit = Parameter(
         'above this limit, lead currents are not driven to 0',
         FloatRange(0, unit='$'), readonly=False, default=99)
 
     _state = None
-    __init = True
     _last_target = None
     switch_time = None, None
 
     def doPoll(self):
-        if self.__init:
-            self.__init = False
-            if self.read_switch_heater() and self.mode == Mode.PERSISTENT:
-                self.read_value()  # check for persistent field mismatch
-                # switch off heater from previous live or manual intervention
-                self.write_target(self.persistent_field)
-            else:
-                self._last_target = self.persistent_field
-        else:
-            self.read_value()
+        self.read_value()
         self._state.cycle()
 
     def checkProperties(self):
@@ -119,6 +109,19 @@ class Magfield(HasLimits, Drivable):
         self.registerCallbacks(self)  # for update_switch_heater
         self._state = StateMachine(logger=self.log, threaded=False, cleanup=self.cleanup_state)
 
+    def startModule(self, start_events):
+        start_events.queue(self.startupCheck)
+        super().startModule(start_events)
+
+    def startupCheck(self):
+        if self.read_switch_heater() and self.mode == Mode.PERSISTENT:
+            self.read_value()  # check for persistent field mismatch
+            # switch off heater from previous live or manual intervention
+            self.write_mode(self.mode)
+            self.write_target(self.persistent_field)
+        else:
+            self._last_target = self.persistent_field
+
     def write_target(self, target):
         self.check_limits(target)
         self.target = target