My Changes so far.

hddfancontrol/__init__.py

@@ -130,6 +130,10 @@ class Drive:
     """ Return True if drive is in low power state, False otherwise. """
     return (self.getState() in (Drive.DriveState.STANDBY, Drive.DriveState.SLEEPING))
 
+  def isUnknown(self):
+    """ Return True if drive is in unknown state, False otherwise. """
+    return self.getState() == Drive.DriveState.UNKNOWN
+
   def getTemperature(self):
     """ Get drive temperature in Celcius using either hddtemp or hdparm. """
     if not self.supports_hitachi_temp_query:
@@ -156,7 +160,8 @@ class Drive:
             temp_unit = drive_data[4]
             if temp_unit != "C":
               raise RuntimeError("hddtemp daemon is not returning temp as Celsius")
-            temp = int(drive_data[3])
+            else:
+              temp = int(drive_data[3])
             found = True
             break
         if not found:
@@ -342,12 +347,12 @@ class Fan:
   def setPwmValue(self, value):
     """ Set fan PWM value. """
     assert(0 <= value <= 255)
-    with open(self.enable_filepath, "r+t") as enable_file:
-      enabled_val = int(enable_file.read().strip())
-      if enabled_val != 1:
-        self.logger.warning("%s was %u, setting it to 1", self.enable_filepath, enabled_val)
-        enable_file.seek(0)
-        enable_file.write("1")
+#    with open(self.enable_filepath, "r+t") as enable_file:
+#      enabled_val = int(enable_file.read().strip())
+#      if enabled_val != 1:
+#        self.logger.warning("%s was %u, setting it to 1", self.enable_filepath, enabled_val)
+#        enable_file.seek(0)
+#        enable_file.write("1")
     self.logger.debug("Setting PWM value to %u" % (value))
     with open(self.pwm_filepath, "wt") as pwm_file:
       pwm_file.write("%u" % (value))
@@ -571,18 +576,28 @@ def main(drive_filepaths, fan_pwm_filepaths, fan_start_values, fan_stop_values,
       # calc max drive temperature
       temps = []
       awakes = []
+      unknowns= []
       for drive in drives:
         awake = not drive.isSleeping()
+        unknown = drive.isUnknown()
+
         awakes.append(awake)
-        if awake or drive.supports_hitachi_temp_query:
-          temps.append(drive.getTemperature())
-        else:
+        unknowns.append(unknown)
+        if (awake and not unknown) or drive.supports_hitachi_temp_query:
+          try:
+            temps.append(drive.getTemperature())
+          except Exception as e:
+            logger.error("Could not get Temperature: " + str(e))
+            temps.append(35)
+        elif not awake:
           logger.debug("Drive %s is in low power state, unable to query temperature" % (drive))
+        else:
+          logger.debug("Drive %s is in unknown state, unable to query temperature" % (drive))
       if temps:
         temp = max(temps)
         logger.info("Maximum drive temperature: %u C" % (temp))
       else:
-        assert(not any(awakes))
+        #assert(not any(awakes))
         logger.info("All drives are in low power state")
 
       if not any(awakes):
@@ -592,6 +607,8 @@ def main(drive_filepaths, fan_pwm_filepaths, fan_start_values, fan_stop_values,
       if temps and (temp > min_temp):
         fan_speed_prct = 100 * (temp - min_temp) // (max_temp - min_temp)
         fan_speed_prct = int(min(fan_speed_prct, 100))
+      elif any(unknowns):
+        fan_speed_prct = 6
       else:
         fan_speed_prct = 0
       fan_speed_prct = max(fan_speed_prct, min_fan_speed_prct)