   }
 
   // If collector is significantly colder than tank, pump is off
-  else if (tank_temp > collector_temp + off_threshold) {
+  else if (collector_temp < tank_temp + off_threshold) {
     //Serial.println("# Collector is colder than tank, pump off");
     no_pump();
   }


float tank_max_temp = 140;      // Deg. F; above this, pump is off
float collector_min_temp = 40;  // Deg. F; below this, pump is off
float on_threshold = 15;        // Deg. F differential before pump turns on
float off_threshold = 0;        // Deg. F differential before pump turns off
int interval = 30000;           // Delay in ms between readings

/*

}

void print_temps(float tank_temp, float collector_temp) {
  Serial.print(tank_temp);
  Serial.print(", ");

