if its broken and makes intermittant contact as u move the wheel that could explain why it works intermittantly.

Have to agree with Magna and Fordman351. Sounds like intermittent connection either behind steering wheel or in the wiring itself. Did you check the brake pressure switch on the side of the master cylinder? This must be low in resistance for the unit to function properly.

Buy a multimeter from d**k Smith, Tandy or Jaycar. Doesn't have to be expensive. Disconnect the servo connector (at the cc unit) and connect the 2 meter probes between pins 5 and 6. Set the meter to the ohms setting. This is what you should read (unlock steering and turn from side to side whilst doing these checks):

No switches depressed:- Open circuit (Infinite resistance)
Off switch pressed:- 5 ohms or less
Resume/coast pressed:- 2090-2310 ohms
+ SET pressed:- 646-714 ohms
- SET pressed:- 114-126 ohms

If any of these readings are out of tolerance or go open circuit whilst turning the steering wheel, the clocksprings will need renewing.