I purchased this timer less than 2 years ago and I am already shopping for a replacement. I do not know what part of the mechanism broke. I do know however that the battery compartment constantly let water in, including when I tried to insulate it with additional layer of silicone. This would kill the 9v battery and the device would go out of commission. I would only notice when the plants started to look half-dead. Overall, it is a garbage product. If I could, I would replace it with another product.