Problem with ardumoto.

Hello guys.

My group is building a treadmill robot using one arduino diecimilanove and one ardumoto driver shield.
But now we are suffering with some problems with ardumoto. I think that we did overpowered our ardumoto and now only one of the DC motors are running correctly in two direction (LOW and HIGH).
The second DC motor (that are connected to port A of ardumoto) only runs in one direction (LOW). I tried to change the DC motors and the second motor worked fine in the B side of ardumoto, so i think the problem is in ardumoto and isn’t on DC motors.

We are using the following code to control the motors:

#include <Wire.h>
#include <nunchuck_funcs.h>

int pwm_a = 3;
int pwm_b = 11;
int dir_a = 12;
int dir_b = 13;

int accx,accy,x,y,zbut,cbut;

void setup()
pinMode(pwm_a, OUTPUT);
pinMode(pwm_b, OUTPUT);
pinMode(dir_a, OUTPUT);
pinMode(dir_b, OUTPUT);
analogWrite(pwm_a, 0);
analogWrite(pwm_b, 0);

void loop ()
analogWrite(pwm_a, 150);
analogWrite(pwm_b, 150);

delay (50);

digitalWrite(dir_a, LOW);
digitalWrite(dir_b, LOW);

I think that code is alright because we just used they early and worked.

Do you guys think what could be the problem?

Thanks to all of you…

Sadly, it sounds very much live you have burnt out one channel of your motor shield. Time to buy a new higher power one? There are other types available, have a look at Ruggedcircuits website.