I have a starter problem. When the key is turn the starter clicked once and nothing, have tried battery booster and jump start with no joy. I then replace starter and noticed a click coming from a small black box on the right side of the engine bay when the key is turn to the 4ht postion. It also clicks intermittently when key is left in the 3rd positon. Any ideas?

ford escort 1.8d 55 van 1998