Power supply wires hot when board is off

I'm using two Pololu Dual VNH5019 Motor Driver Shields powered with a 55 amp max external power supply.

When I plug the power supply in, without either shield or arduino on, the 10 gauge power wires get warm very quickly. I would think that nothing would get warm until I actually plug in some motors and start using the motor shields. Do I have a short somewhere or is this normal? The motor shield jumpers to power the arduinos are not installed so the external power supply is for the motors only.

Turns out the 'pass-through' terminal block I was using for the power supply wires paired the terminals together so there was a short circuit right at the beginning :(