My issue us that the motor driver seems to be blocking nearly all of the current from getting to the motors. I've checked the current running from the batteries to the motor (bypassing the shield) and that is coming out at about .65A, which is ok for what I need. However, for some reason the shield is not routing any power what so ever to the M1 motor attachment points.
Does anyone have any idea why this is and what I can do to solve it?
What is your software? Did you try an Adafruit example. The chip will certainly 'block' the voltage if it receives incorrect logic signals. What about M2?
The power source for the motors is a battery of 6 1.5V cells, attached via a breadboard into the ext_pwr sockets on the shield. I know the breadboard isn't blocking the current as I've tested that.
And yes I have tried several Adafruit examples, there is no difference. I have tried M1, M2, M3 and M4 with no luck.
So I've done a bit of investigating and I've solved the first problem. However, I now have a second problem. The motors are rated at 7V, however, only 1V is getting through to the motor, even though 8V is going into the shield.
You should explain the source of the 1st problem. It may be relevant to the second.
You have not posted your sofware. Are you using PWM?
A low PWM duty cycle may show up on the DC voltmeter as a low voltage since the meter is a roughly averaging the pulses.