diff --git a/cnc/config.py b/cnc/config.py
index 3c205ac..6e41c7d 100644
--- a/cnc/config.py
+++ b/cnc/config.py
@@ -89,3 +89,6 @@ INSTANT_RUN = True
 # velocity would be decreased(proportional for all axises) to fit the maximum
 # velocity.
 AUTO_VELOCITY_ADJUSTMENT = True
+
+# Automatically turn on fan when extruder is heating, boolean value.
+AUTO_FAN_ON = True
diff --git a/cnc/gmachine.py b/cnc/gmachine.py
index 5db3f45..6403ced 100644
--- a/cnc/gmachine.py
+++ b/cnc/gmachine.py
@@ -18,6 +18,8 @@ class GMachine(object):
     """ Main object which control and keep state of whole machine: steppers,
         spindle, extruder etc
     """
+    AUTO_FAN_ON = AUTO_FAN_ON
+
     def __init__(self):
         """ Initialization.
         """
@@ -85,6 +87,8 @@ class GMachine(object):
             self._heaters[heater].stop()
             del self._heaters[heater]
         if temperature != 0:
+            if heater == HEATER_EXTRUDER and self.AUTO_FAN_ON:
+                self._fan(True)
             self._heaters[heater] = Heater(temperature, coefficients, measure,
                                            control)
             if wait:
diff --git a/tests/test_gmachine.py b/tests/test_gmachine.py
index 901ec56..8efc0e1 100644
--- a/tests/test_gmachine.py
+++ b/tests/test_gmachine.py
@@ -268,6 +268,15 @@ class TestGMachine(unittest.TestCase):
         self.assertTrue(m.fan_state())
         m.do_command(GCode.parse_line("M107"))
         self.assertFalse(m.fan_state())
+        # check auto fan feature
+        m.AUTO_FAN_ON = True
+        m.do_command(GCode.parse_line("M104S" + str(MIN_TEMPERATURE)))
+        self.assertTrue(m.fan_state())
+        m.do_command(GCode.parse_line("M104S0"))
+        self.assertTrue(m.fan_state())
+        m.do_command(GCode.parse_line("M107"))
+        self.assertFalse(m.fan_state())
+        m.AUTO_FAN_ON = False
 
     def test_m140_m190(self):
         m = GMachine()