I installed the Grote 44040 DRL (American TL requires DRL for Canadian import) and it worked. I go back to it some four hours later and the car battery is completely dead. I didn't leave any doors open or lights on and the keys were with me. My question is......can bad wiring cause a car battery to completely drain? The lights and horn would not work, not even the radio would turn on.

 

It's not going to drain if the ligts are off. Possinby the battery was weak and when working on the lights with the ignition on with testing and what not, the battery ran down. If this si not the case, you'll need to check the battery for any draw when the ignition is off.

Just something I chose at random:
http://automotivemileposts.com/garage/v3n2.html