I have a 2005 mazda 3 sedan.

The cruise control has been playing up for a while now. Sometimes it works fine but mostly it turns on ok but will turn itself off randomly. I'll be driving down the freeway happily cruising when the green light will turn orange by itself and the cruise will disengage. Occassionally, and more worryingly, after using the cruise and setting it to coast, it will turn itself back on again.

This has been mentioned on the past 2 service visits. Both time they said they could not replicate the issue while driving down their street at 30kph. Duh! The first visit they eventually replace the cruise after I insisted it was faulty and the new one did the same thing. They replaced it twice more with the same results.

The more recent service visit I didn't bother hastling them after they told me it was fine because they obviously we're insterested in testing it properly.

Has anyone come across anything like this before?

 

Sorry you're having problems with your cruise. Do you know what they replaced? I can't comment on why your cruise is turning off by itself. The only times the cruise should disengage are: if you push OFF or cancel on the wheel, when you press the brake, or when you engage the clutch (on a MTX). If you're not doing one of those things then it should stay on.

As for turning back on after setting it to coast I think you may be misunderstanding how that feature works. With the cruise set and running pressing coast will decrease the set speed by 1-2mph..... Alternately if you push and hold coast it will stay off until you release it. It's really difficult to gauge what it will end up set at when you release the button, so I don't really suggest that...... if I'm changing my speed more than five mph I just hit cancel and then SET once I get to the speed I want. The coast button basically does the same thing as the accelrate button only for slowing down instead of speeding up. I find that pushing either button four times will change your speed about five mph

 

I'm not sure exactly what they replaced, they just said they replaced the cruise control unit. I'm definitely not cancelling or pressing the brake when it turns off and pressing off would turn it off completely but its just going to orange.

Yeah I meant after pressing the cancel button, not the coast button. Its called coast in my work car so I got mixed up. I press cancel, the led goes orange and maybe 10 seconds later it turns on again (goes green) and the car takes over the acceleration. It only happens rarely but still happens.

 

Since the actuator unit is working, and the dealer replaced the control unit, get a spray can of electrical contact cleaner/lubricant and squirt it into the spaces between the switches and the panel in the steering wheel cruise control insert. Your problem is either this switch assembly or possibly a broken conductor in the clockwork spring cable takeup mechanism where the steering column cables emerge to connect to the car chassis wiring.
Meantime play safe and keep that thing off.