Anyone had trouble with their cruise control??

Mine worked for the first few times I tried it, but would "drop out" after like 30 secs. Now it just does not work at all.

Cant figure out if a mechanical or electrical problem??

Under the dash, the release valves on the clutch and brake are working ok, and so too the accelorator "pump"..

Vacuum pump under bonnet is all connected, but dont know how to tell if it is working??

Any thoughts?