VNH5019 + Uno - only one motor working


I just received my dual VNH5019. It’s mounted on an Arduino Uno and drives 2* 12V 29:1 Pololu motors.

I installed the library and all. When I run the Demo, only the motor connected to M2 is working. M1 motor doesn’t do anything. No sound, leds on M1 screw terminals don’t light up.

If I reverse the two motors then the other motor works, i.e. it’s not a motor problem, both are working.

When I run the Demo code I don’t get any faults, it simply says “M1 current = 0”. M2 current looks OK.

When I run the Demo with motors disconnected, then LEDs of both M1 and M2 light up properly. I checked the voltage on the screw terminals using a multimeter. M2 look good (+11V and -11V using 8 NiMH batteries fully charged). However M1 voltages are only +3.2 to -3.2V. Voltages follow PWM perfectly, but are “scaled down” to 3.2V.

I have a barebones setup, only the Uno powered by a 9V battery, and the shield on top powered by 8x NiMH AA batteries (they are fully charged and give about 11V at the moment). Nothing else connected and just running the original Demo sketch.

I don’t know where the low voltage on M1 comes from. I’d appreciate any help, thanks!


I am sorry you are having trouble with your VNH5019 shield. Can you post some pictures of your setup? It would be useful to post pictures that show both sides of the board and all of your connections.


OK I think I solved it actually :slight_smile:

I checked all pins with the multimeter for shorts and/or continuity. I found that Pin 9 had continuity on the Arduino only, and on the shield only, but no continuity when the shield was plugged on the arduino (ie, from underneath the arduino to the header on top of the shield).

I resoldered the “bar” of headers and now I get proper pin continuity on all pins, and both motors work (correct tension on M1 and M2 terminals).

I also found that if I push the shield to the max on top of the Arduino (headers all the way) the connection is actually worse than if I pull back a bit (like 2mm). Strange, but hey, it works.

Thanks for the help.

Thanks for letting us know how you solved it.

By the way, getting a worse connection by pushing your shield into your Arduino doesn’t sound good. If you post pictures of your board, I could help you figure out what might be causing this behavior.


Hi Jonathan,

thanks for the help. I identified the headers were bad on the Arduino side actually (I tried a different shield and had the same problem). I replaced the female jumpers on the arduino and now everything is fine. Thanks again.