I have an older Cat M20 forklift that I just bought. It runs good except when I push the floor pedal in either directions it just goes to full power. When I let off the pedal, there is a spark that I can see from the back battery cover. It looks like the switch or whatever it is, is stuck. It just goes from full power to off. I thought these were supposed to move faster as you push the pedal further and vice versa when you let off. Can anyone tell me what that part that controls forward or reverse movement is called? Is this a common problem? The electric forklift is rated for 2000 lbs.