diff --git a/src/thermostat.c b/src/thermostat.c
--- a/src/thermostat.c
+++ b/src/thermostat.c
@@ -3,8 +3,10 @@
 //
 
 #include "thermostat.h"
+#include "gpio.h"
 
-// PID implementation
+// Thermostatic control implementation
+static uint8_t thermostat_plant_on = 0;
 
 float thermostat_process(void)
 {
@@ -15,23 +17,28 @@ float thermostat_process(void)
     //			max31855_readtemp(spi_get(), &set, &status); // Read MAX31855
     //			#endif
 
-    float ssr_output = 0.0;
-    uint8_t thermostat_plant_on = 0;
 
     // TODO: Migrate this FxP conversion to the readtemp code or similar
-    float temp = runtime_status()->temp;
-
+    float temp = runtime_status()->temp; // (scale to whole degrees)
+    uint32_t hyst = flash_getsettings()->val.hysteresis;
 
     // EMZ FIXME: This could be way simpler
-    if(flash_getsettings()->val.plant_type == PLANT_HEATER && runtime_status()->setpoint * 10 < temp - flash_getsettings()->val.hysteresis * 10)
-        thermostat_plant_on = 1;
-    else if(flash_getsettings()->val.plant_type == PLANT_HEATER && runtime_status()->setpoint * 10 > temp + flash_getsettings()->val.hysteresis * 10)
-        thermostat_plant_on = 0;
 
-    if(flash_getsettings()->val.plant_type == PLANT_COOLER && runtime_status()->setpoint * 10 > temp + flash_getsettings()->val.hysteresis * 10)
-        thermostat_plant_on = 1;
-    else if(flash_getsettings()->val.plant_type == PLANT_COOLER && runtime_status()->setpoint * 10 < temp - flash_getsettings()->val.hysteresis * 10)
-        thermostat_plant_on = 0;
+    if(flash_getsettings()->val.plant_type == PLANT_HEATER)
+    {
+    	if(temp < runtime_status()->setpoint - hyst)
+        		thermostat_plant_on = 1;
+    	if(temp > runtime_status()->setpoint + hyst)
+    		thermostat_plant_on = 0;
+    }
+
+    if(flash_getsettings()->val.plant_type == PLANT_COOLER)
+	{
+    	if(temp < runtime_status()->setpoint - hyst)
+			thermostat_plant_on = 0;
+    	if(temp > runtime_status()->setpoint + hyst)
+    		thermostat_plant_on = 1;
+	}
 
     // EMZ: TODO: Refactor to output_enabled or something
     if(runtime_status()->pid_enabled && thermostat_plant_on)
@@ -40,21 +47,24 @@ float thermostat_process(void)
         // put ssr output on display
         ssd1306_drawstring("      ", 0, 90); //fixme: this is bad, but I can't get the old digits to clear otherwise
         char tempstr[6];
-        itoa(ssr_output, tempstr, 10);
+        itoa(thermostat_plant_on, tempstr, 10);
         ssd1306_drawstring(tempstr, 0, 90);
 
 
 
-        //                HAL_GPIO_WritePin(SSR_PIN, 1);
+		HAL_GPIO_WritePin(SSR, 1);
         HAL_GPIO_WritePin(LED, 1);
     }
     else
     {
-        //                HAL_GPIO_WritePin(SSR_PIN, 0);
-        HAL_GPIO_WritePin(LED, 0);
+		HAL_GPIO_WritePin(SSR, 0);
+		HAL_GPIO_WritePin(LED, 0);
     }
 
-    return ssr_output;
+    if(thermostat_plant_on)
+    	return 1000.0f;
+    else
+    	return 0.0f;
 }