Transmission line plays important roles in delivering electric energy from generation site closer to the customer. Failure of a transmission line can cause significant economic loss due to undelivered energy and may lead to catastrophic system black out. One critical part of transmission line is dead end connector, thus ensuring good condition of transmission line dead end connector is critical to avoid extensive losses. This paper investigates the cause of failure of dead end connectors that were installed in 150 kV ACSR lines. The failed connectors were examined and tested to find out the cause of the breakdown. Several samples of suspected bad connectors are also tested for comparison. Simulations using finite element software were conducted to provide broader insight on failure propagation. The investigation found that the dead end connectors were failed due to high current flowing through the steel part of the conductor which is caused by high contact resistance between the aluminium part of the conductor and the connector. Further study is needed to mitigate similar condition to occur in the dead end connector installation.