diff -r b56988cc516b -r ba340e00aab2 thermferm/mqtt.c
--- a/thermferm/mqtt.c	Sun Mar 31 13:57:25 2019 +0200
+++ b/thermferm/mqtt.c	Sat Apr 27 15:36:16 2019 +0200
@@ -257,7 +257,7 @@
 						/* Allways turn everything off after a mode change */
 						unit->PID_cool->OutP = unit->PID_heat->OutP = 0.0;
 						unit->PID_cool->Mode = unit->PID_heat->Mode = PID_MODE_NONE;
-						unit->heater_state = unit->cooler_state = unit->fan_state = unit->light_state = 0;
+						unit->heater_state = unit->cooler_state = unit->fan_state = unit->light_state = unit->light_timer = 0;
 						unit->heater_wait = unit->cooler_wait = unit->fan_wait = unit->light_wait = 0;
 						device_out(unit->heater_address, unit->heater_state);
 						device_out(unit->cooler_address, unit->cooler_state);
@@ -336,12 +336,16 @@
 				    }
 				}
 
-				if ((json_object_object_get_ex(metric, "light", &setpoint)) && (unit->mode == UNITMODE_NONE)) {
+				if (json_object_object_get_ex(metric, "light", &setpoint)) {
 				    if (json_object_object_get_ex(setpoint, "state", &val)) {
-					if (json_object_get_int(val) != unit->light_state) {
-					    unit->light_state = json_object_get_int(val);
-					    unit->mqtt_flag |= MQTT_FLAG_DATA;
-					    syslog(LOG_NOTICE, "DCMD change fermenter %s: light_state to %d", message_alias, unit->light_state);
+					if (json_object_get_int(val) > 0) {
+					    unit->light_timer = 300;	// 5 minutes
+					    syslog(LOG_NOTICE, "DCMD set fermenter %s: light_timer 300", message_alias);
+					    if (!unit->light_state) {
+					    	unit->light_state = 1;
+					    	unit->mqtt_flag |= MQTT_FLAG_DATA;
+					    	syslog(LOG_NOTICE, "DCMD change fermenter %s: light_state to %d", message_alias, unit->light_state);
+					    }
 					}
 				    }
 				}