I can set my cruise and it will eork fine until I go up a hill.If I keep my foot on it it will stay set.I can feel the pedal moving by itself by barely touching it.I have changed all the vaccum lines that I can see.Can it be switch on the column,or the switch behind the brake pedal,or the servo?Can it still be a vaccum?The reason I ask that is because of my bad master cyclinder and how my blower on my heater/ac controls give me problems about blowing hard.

 

Well the cruise is operated by vac, thats how it pulls the throttle open...

By your description i gather that it doesnt have enough 'umph' to pull the throttle open more?

So first things first, verify that you are getting good vac. or maybe the diaphram has a hole in it or something.

 

Do you think that if I replace the master cyclinder that may help?The cruise servo is about 300. bucks new.the parts are getting hard to find at the junk yard down here.

 

the brakes have nothing to do with the cruise control, other than to shut it off when brakes are applied.

All the cruise does is pull the throttle!