I plug a4988 driver on to ramps 1.4 and then ramps onto Arduino mega to check the voltage the driver gives out. Then I connect 12v 16.67a power supply and check the diver which only gives 0.26V at max when I have fully turned it in the clockwise direction. What could be the issue?
Can you clarify what you are trying to measure and post some pictures of your setup that show your driver and all of your connections? Close-up pictures of both sides of the driver would be helpful too.