davway

was having a think today why the cruise in the ZL was working for 2 days then stopped after i ran over a pothole. my theory doesnt exactly relate around the pothole but brings up quiet a good point which i will need a few answers about.

when cruise control is activated it can be disengaged by pressing the brakes. now if you had brake(s) that were sticking then the system would think you are pressing the brakes and not allow it to work. would this be correct? i noticed today that when i was coming down the driveway i was getting brake squeal BUT i wasnt on the brakes which made me think of this.
this theory may be all well but im lacking some facts about the cruise system, specifically how does the system know that you have pressed the brakes? is there a sensor in the brake calipers (front and/or back)or somewhere along the brake line? or is there a switch behind the brake pedal that when pushed it knows to shut it off. i found 2 switches behind the pedal but i believe they are both for the brake lights as there are 4 globes for the lights (1 switch= 2 globes) and only 1 switch in the van for 2 globes.
if the sensors are in the calipers (or the brake area) would i be right in assuming that if there is sticking brake(s) that it would think i am braking and not allow it to work?

any input into this would be appreciated.

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needturbo6

it is the brake light switch the cruise control unit uses.
i checked in my xf manual to be sure.

and just to clear it up, to my knowledge there is only one brake light switch on every car, i dunno about trucks though

deankdx

in answer to your question as i have installed(recently removed to fit to my XG ute) an XF cruise control set up to my XE. have removed a ZL/XFghia one also.
the brake switch does turn the cruise off(if you chop the wires and have them the wrong way around this also gives the same affect[yep i did it])
i'm sure i have seen two switces on a pedal box but don't know why? backup perhaps??
cluth pedal should have one also(as i found out if you want to change gear the engine revs its nuts off trying to maintain speed) i never got around to fitting this switch to cluch but was concious of potential problem.
there is about four different point of conection to looms for cruise system, so i would assume you may need to check these points (mabe rubbimg on metal somewhere and shorting out???)
thats all i can think of for now

davway

thank you both for your answers. now another question has arisen from this info. i personally havent checked this myelf but this is what the auto elec done: (with some background for those that dont know)

cruise hasnt worked for over a year. brake lights stopped working within the last month. power at the brake pedal switches but no power at the tail lights. (this i know)

auto elec suggested there was a broken wire somewhere in the car and opted instead to rewire the brakes from the pedal to the lights. brake lights work and miraculously so does the cruise (till i hit a pothole). so without actually looking at the wiring the elecs done how would this affect what both of you have said?

i will look at what has been done from the elecs tomorrow but something just isnt adding up here and i want to get to the bottom of this.

sticky brakes have nothing to do with this at all?

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deankdx

auto elec suggested there was a broken wire somewhere in the car and opted instead to rewire the brakes from the pedal to the lights. brake lights work and miraculously so does the cruise (till i hit a pothole). so without actually looking at the wiring the elecs done how would this affect what both of you have said?

unless theres insulation missing from a wire and shorting out still could possibly cause this fault(rubbing on something)(1 of my XEs caught fire from this in the engine bay NOT FUNNY )
i would still think it would be connectors as they can get like a tarnish on them and maybe auto elec moved(wiggled) wires by accident while rewiring stop light s
just a thought (i'm drunk)