Intermittent Cruise Control

[Cloppydog2]

I have just bought an 18 plate B9 van with 106,000 on the clock. I am a courier that does around 100,000 mile per year so CC is not just a nicety, but an absolute necessity. Recently (only had the van for 3 weeks but still racked up 8000 miles)I am having a problem of activation. Sometimes it will activate and sometimes it won't. When it is activated it works fine until I cancel it then it is a lottery whether or not if I can re-establish CC. Checked the Diagbox and it only lists the cause of de-activation which is always "Brake Application". I realise that CC is quite a complex system involving lots of other qualifying parameters, does anybody have clues to where I should be looking for problems. Local puggy garage can look at it in 3 weeks!!!!

[deejay_xb]

replace brake pedal switch

[saskak]

Exactly what deejay_xb said. I had very similar on the M59 1.6HDi. The cruise was intermittent, sometimes it worked, sometimes not. I replaced the brake light switch and the cruise started worked again constantly. In these intermittent cases, most likely your rear stop lights are not working as well, a bit dangerous if you are stopping and the people at the back do not see it.

[Sol]

To cancel the cruise, the rear brake light switch has to be engaging and flicking the lights on. If they never came on, the system would have no idea you were braking. Cruise would always work.

The switch is adjustable and is probably needing pulled out further than it currently is. The plunger has steps in it, if only 2 are showing then pull the head till it clicks out a couple of notches and try that.

The switch is on your passenger side under a large square cover, held by two very deep set 10mm nuts. The switch unlocks anti clockwise, leave the little red bit alone, (you'll see what I mean) and just pull the plunger firmly but gently, out till 4 ridges are showing and try that.

Get an assistant to press the pedal down while you reinsert the switch or it may get pushed back to where it was. Once locked in, release the pedal.

The switch itself is very well made and reliable. The plunger gets pushed back occasionally and needs reset. Could be getting boots under the brake pedal while getting in. Below is mine before I adjusted it. No more trouble since. My brake lights were flickering constantly.

[saskak]

To cancel the cruise, the rear brake light switch has to be engaging and flicking the lights on. If they never came on, the system would have no idea you were braking. Cruise would always work.

The switch is adjustable and is probably needing pulled out further than it currently is. The plunger has steps in it, if only 2 are showing then pull the head till it clicks out a couple of notches and try that.

The switch is on your passenger side under a large square cover, held by two very deep set 10mm nuts. The switch unlocks anti clockwise, leave the little red bit alone, (you'll see what I mean) and just pull the plunger firmly but gently, out till 4 ridges are showing and try that.

Get an assistant to press the pedal down while you reinsert the switch or it may get pushed back to where it was. Once locked in, release the pedal.

The switch itself is very well made and reliable. The plunger gets pushed back occasionally and needs reset. Could be getting boots under the brake pedal while getting in. Below is mine before I adjusted it. No more trouble since. My brake lights were flickering constantly.

Despite them being well made they can fail, my problem was not the length of the plunger. The resistance between the 1st & 2nd pins was ~0.3ohms rather than 0 when not pressed. If I played around with it, plunging and releasing the switch outside of the car eventually it was reading 0/1, but then it will go back to ~0.3ohms. Not saying that this is the OP's problem.

[Sol]

Yeah could be either mate. I adjusted mine as it's not possible to just go and get one here and no brake lights is no go at all.

They are only a tenner mind you.

But if the only issue is the cruise then it's worth trying adjustment first. It's free and is the same hassle as changing it over. On the B9 the nuts need a tube spanner to reach them. It is a complete pig of a job.

[Cloppydog2]

Thanks everybody for chipping in with this problem, ordered a new switch (@£13) and fitted it. "Jobs a good un".

[Cloppydog2]

Yeah could be either mate. I adjusted mine as it's not possible to just go and get one here and no brake lights is no go at all.

They are only a tenner mind you.

But if the only issue is the cruise then it's worth trying adjustment first. It's free and is the same hassle as changing it over. On the B9 the nuts need a tube spanner to reach them. It is a complete pig of a job.

agree with you on that one Zion, it is as if they are "locknuts". No chance of spinning them off>

[Sol]

Yeah could be either mate. I adjusted mine as it's not possible to just go and get one here and no brake lights is no go at all.

They are only a tenner mind you.

But if the only issue is the cruise then it's worth trying adjustment first. It's free and is the same hassle as changing it over. On the B9 the nuts need a tube spanner to reach them. It is a complete pig of a job.

agree with you on that one Zion, it is as if they are "locknuts". No chance of spinning them off>

And the fact they are in a deep tube - impossible to reach with a normal socket or spanner. Yeah they are like those clever Japanese locknuts used on exhaust fittings, no sign of any locking material - just a little set of cuts on the face, yet they will fight to the last thread.