I want to switch out the taillights on my '80 Malibu for 1981 taillights. I have the taillights and the 1981 taillight harness. I installed the '81 harness, and when I connect the battery, the brake and signal filaments in the 4 taillight bulbs come on steady and stay on. This happens as soon as I connect the battery, without turning anything on. The connectors on both the '80 and '81 harnesses look the same, the wire colours are the same, the connectors connect to the vehicle harness connector in the trunk the same. I've tried 2 different sets of bulbs with no difference. Any ideas? Thanks in advance.