97 Achieva Cruise Control not working

Over several months my cruise control stopped working.
Symptoms: I started the car from cold and the cruise control does not work. The switch was in the "on" position but setting a speed did not work. I would try to set a speed with no results until I had driven approximately 10 miles. Then I would set a speed and it would work. If I braked, I could resume speed. If I turned off the cruise control and then turned it back on it might or might not work.
Over three months the cruise control worked less and less often. Now it does not work at any time.
Could someone guide me to things to check in the car, or possibly replace. I'd rather try myself than pay someone else.
The car is a 1997 Achieva 2.4 liter SL, 39,000 miles on car, Was only driven 27,000 miles the first 10 years, crank windows, power locks, Auto Trans, The heater core was changed prior to the cruise control problem. The airbag light is on all the time but that did not seem to happen at the same time the cruise went out.

Thanks for your help.:cool: