Aftermarket controllers are the brain of any electric golf cart after about the year 2000. Before that, it was varying gauges of coiled wire that, thru resistance, metered the rate of acceleration. They were very heat-sensitive systems and prone to failure. With the way golf carts get punished these days, the industry had to act. They needed to increase the reliability of power delivery to the motor. The answer to all these issues became controllers. This E-Z-GO 350-Amp PDS Curtis Controller is an excellent example of the leaps and bounds the industry has taken in this field.The motor on your golf cart is a giant magnet. It needs both a positive and negative charge to spin, which is what turns the wheels. The positive supply is constant, while this OEM replacement controller sends a building or variable negative as you depress the accelerator. Without a working controller, you cannot get a negative signal to your motor, and therefore your golf cart won't run. Controllers are arguably the most critical piece of equipment on your EZGO. Make sure you buy a quality unit from Buggies Unlimited and protect your investment.