diff --git a/sys/powerpc/powermac/powermac_thermal.c b/sys/powerpc/powermac/powermac_thermal.c
index 250c9f0..725482b 100644
--- a/sys/powerpc/powermac/powermac_thermal.c
+++ b/sys/powerpc/powermac/powermac_thermal.c
@@ -43,7 +43,7 @@ __FBSDID("$FreeBSD$");
 #include "powermac_thermal.h"
 
 /* A 10 second timer for spinning down fans. */
-#define FAN_HYSTERESIS_TIMER	10
+#define FAN_HYSTERESIS_TIMER	30
 
 static void fan_management_proc(void);
 static void pmac_therm_manage_fans(void);
@@ -143,10 +143,10 @@ pmac_therm_manage_fans(void)
 		average_excess = max_excess_zone = 0;
 		SLIST_FOREACH(sensor, &sensors, entries) {
 			temp = imin(sensor->last_val,
-			    sensor->sensor->max_temp);
+			    sensor->sensor->high_temp);
 			frac_excess = (temp -
 			    sensor->sensor->target_temp)*100 /
-			    (sensor->sensor->max_temp - temp + 1);
+			    (sensor->sensor->high_temp - temp + 1);
 			if (frac_excess < 0)
 				frac_excess = 0;
 			if (sensor->sensor->zone == fan->fan->zone) {
diff --git a/sys/powerpc/powermac/powermac_thermal.h b/sys/powerpc/powermac/powermac_thermal.h
index 424c612..1059f95 100644
--- a/sys/powerpc/powermac/powermac_thermal.h
+++ b/sys/powerpc/powermac/powermac_thermal.h
@@ -42,7 +42,7 @@ struct pmac_fan {
 };
 
 struct pmac_therm {
-	int target_temp, max_temp;	/* Tenths of a degree K */
+	int target_temp, high_temp, max_temp;	/* Tenths of a degree K */
 	
 	char name[32];
 	int zone;
diff --git a/sys/powerpc/powermac/smu.c b/sys/powerpc/powermac/smu.c
index cbc0e35..d7c9db7 100644
--- a/sys/powerpc/powermac/smu.c
+++ b/sys/powerpc/powermac/smu.c
@@ -1245,8 +1245,9 @@ smu_attach_sensors(device_t dev, phandle_t sensroot)
 
 		if (sens->type == SMU_TEMP_SENSOR) {
 			/* Make up some numbers */
-			sens->therm.target_temp = 500 + 2732; /* 50 C */
-			sens->therm.max_temp = 900 + 2732; /* 90 C */
+			sens->therm.target_temp = 400 + 2732; /* 40 C */
+           sens->therm.high_temp = 750 + 2732; /* 75 C */
+           sens->therm.max_temp = 950 + 2732; /* 95 C */
 
 			sens->therm.read =
 			    (int (*)(struct pmac_therm *))smu_sensor_read;
diff --git a/sys/powerpc/powermac/smusat.c b/sys/powerpc/powermac/smusat.c
index 2e37ae4..5dbb73c 100644
--- a/sys/powerpc/powermac/smusat.c
+++ b/sys/powerpc/powermac/smusat.c
@@ -184,8 +184,9 @@ smusat_attach(device_t dev)
 
 		if (sens->type == SMU_TEMP_SENSOR) {
 			/* Make up some numbers */
-			sens->therm.target_temp = 500 + 2732; /* 50 C */
-			sens->therm.max_temp = 900 + 2732; /* 90 C */
+			sens->therm.target_temp = 400 + 2732; /* 40 C */
+			sens->therm.high_temp = 750 + 2732; /* 75 C */
+			sens->therm.max_temp = 950 + 2732; /* 95 C */
 			sens->therm.read =
 			    (int (*)(struct pmac_therm *))smusat_sensor_read;
 			pmac_thermal_sensor_register(&sens->therm);