diff -r 0ab5c3fd7c77 -r ffc4b8aa824f thermferm/thermferm.c
--- a/thermferm/thermferm.c	Wed Apr 01 15:20:05 2015 +0200
+++ b/thermferm/thermferm.c	Wed Apr 01 15:56:04 2015 +0200
@@ -1432,16 +1432,13 @@
 			}
 			device_out(unit->cooler_address, unit->cooler_state);
 		    }
-		    if (unit->heater_address && unit->cooler_address && unit->fan_address) {
+
+		    if ((unit->heater_address || unit->cooler_address) && unit->fan_address) {
 			/*
-			 * If the temperature difference between air and beer is more then
-			 * xxx degrees, turn the fan on to make an airflow.
-			 * Maybe, run the fan too if the heater is on because the heater in
-			 * most cases will be some sort of radiating heat device.
-			 * For cooling ??? dunno yet.
+			 * If there is a heater or cooler and we have a fan, turn fan on if
+			 * cooling or heating.
 			 */
-			if (((unit->air_temperature - unit->beer_temperature) > 1000) ||
-				((unit->air_temperature - unit->beer_temperature) < -1000)) {
+			if ((unit->heater_address && unit->heater_state) || (unit->cooler_address && unit->cooler_state)) {
 			    if (! unit->fan_state)
 				syslog(LOG_NOTICE, "Fan Off => On");
 			    unit->fan_state = 100;
@@ -1452,6 +1449,7 @@
 			}
 			device_out(unit->fan_address, unit->fan_state);
 		    }
+
 		} else {
 		    P_err = 0.0;
 		    unit->PID_iState = 0.0;