This will be either a defective pump or the wrong power supply, the controller is starved for power so it is cycling off and on. Verify that the power supply connected is labeled Tunze 5012.010. If that is correct, it has to be the pump and we can send a replacement.
Email me a copy of the receipt, Tunze At sbcglobal dot net and we will get a pump out to you. Pump failures tend to be random, they usually last 2-3 years.