Hillbilly2, I'm in total agreement with you in regard to it just having to be a short of some sort. It certainly acts like a short. I will let everyone know in the next day or so what I can determine.

At this point there are only two variables;
1. led bulbs in place of the incandesents
2. The LED's may be in backwards (off 180 degrees)

The back of the package does indicate if the led does not light put it in the other way due to specific polarity.

It also indicates guaranteed lighting from 10.5 volts to 15.8volts.

It does appear to have some sort of resistor in line.