Update generic_thermostat.py

As suggested, I added a callback on the heater switch state change.
Still it doesn't solve the problem.

homeassistant/components/climate/generic_thermostat.py

@@ -5,7 +5,6 @@ For more details about this platform, please refer to the documentation at
 https://home-assistant.io/components/climate.generic_thermostat/
 """
 import logging
-import time
 
 import voluptuous as vol
 
@@ -88,6 +87,7 @@ class GenericThermostat(ClimateDevice):
         self._unit = hass.config.units.temperature_unit
 
         track_state_change(hass, sensor_entity_id, self._sensor_changed)
+        track_state_change(hass, heater_entity_id, self._switch_changed)
 
         sensor_state = hass.states.get(sensor_entity_id)
         if sensor_state:
@@ -166,6 +166,12 @@ class GenericThermostat(ClimateDevice):
         self._control_heating()
         self.schedule_update_ha_state()
 
+    def _switch_changed(self, entity_id, old_state, new_state):
+        """Called when heater switch changes state."""
+        if new_state is None:
+            return
+        self.schedule_update_ha_state()
+
     def _update_temp(self, state):
         """Update thermostat with latest state from sensor."""
         unit = state.attributes.get(ATTR_UNIT_OF_MEASUREMENT)
@@ -223,7 +229,6 @@ class GenericThermostat(ClimateDevice):
                 if too_cold:
                     _LOGGER.info('Turning on heater %s', self.heater_entity_id)
                     switch.turn_on(self.hass, self.heater_entity_id)
-        time.sleep(.1)
 
     @property
     def _is_device_active(self):