Motionsensor changes between high and low constantly

Hello,
i have this motionsensor and connected it to my arduino. i have the - pin in ground, the vcc pin in 5v and the output pin in any digital pin (i tried different ones). My Code looks like this:

int sensor = 7;
int bewegungsstatus=0;

void setup() {
  pinMode(sensor, INPUT);
  Serial.begin(9600);
}

void loop() {
  bewegungsstatus = digitalRead(sensor);
  if(bewegungsstatus == HIGH){
    Serial.println("High");
  }else{
    Serial.println("Low");
  }
  delay(100);
}

In the Serial Monitor it goes low for some seconds, turns high again and after some seconds its low again. The delay is always about the same. Even if i do not connect ground and 5v it still has this low, high, … pattern. If i unplug the output pin the pattern stops.
Any ideas what causes this problem?

Have you tried adjusting the sensitivity and timeout settings? If so, in setup() try:

pinMode(sensor, INPUT_PULLUP);

Also , did you try changing the "REPEAT" jumper?