2008 Freightliner Columbia cruise control problem

There's also a Brake Pedal Switch for the Cruise Control that you need to check out.

 

If no micro switch for brake then it is actuated with the brake pressure switch that operates your brake lights. Usually switch operates relay which operates the lights thru fuses. On a 2000 Volvo that pressure switch if behind the dash. Push your brakes and hold them in with a pipe or hammer or something. See if you have brake lights. If you have brake lights then the brake pressure switch is working correctly.

 

That condition sounds like your cruise switch is going bad. Is the switch on your blinker arm or a button on your steering wheel. If on your blinker switch.....or an actual on/off switch.....do this. Turn cruise on going down the road. Wiggle the on/off switch when your cruise is on.....not hard enough to operate it to the off position but enough to see if the switch is worn/bad. That is what I would do to futher the troubleshooting in this case. Good day.
Are you losing speed indication at all during this process? Do you know where your speed sensor is located on your transmission/drive train?

 

Did you ever find the problem?