Cruise control issue

Having an issue with my cruise control on 87 Fifth. Car has not been driven much for at least the last two years. I have used the cruise in the past and it seemed to work fine. Now when engaged, to set the speed it just accelerates the car. I have only driven in town and have not seen how far the car may accelerate. The FSM does not seem to address this issue. I'm wondering if it might be in the switch. I hope someone can give some advice.