Controlling Joints

[Mezillious]

Hi, I am having a bit of trouble controlling joints using keys. I have made a car with wheels that spin when the slider bar is dragged to 1 and a steering arm that rotates with a separate slider bar.
My problem is, when I set the controls to keys and run the simulation, the steering axle locks to the left and the wheels beginning spinning in crazy directions. Can I not bind a key to the same operation as a slider? For example, X = accelerate, A = rotate steering arm left, D = rotate steering arm right.

Thanks,
Mezillious