Honestly Im not too sure if this caused it or it was a coincidence as the light only came! on for a bit and then went out but I can see how a spring snapping could cause the brakes to become just uneven enough for it to set off the warning but either way kudos to the xf for giving me some kind of warning!

that's the first time I've ever seen a reason for that light to come on, and the fact it worked is equally impressive.    great to see @bear351c on the ball with this one,  I've seen brake pads (discs) worn down to metal and not caused that light to come on     

I've got this on My to do list, so will update with My version once done, but would like to confirm the tips below. 

If anyone has any other info tips or links to fitting cruise control to a forte series 3 AU (has ABS) I'd be interested before I go investigating any further on My own.(Mine is a wagon, so the combination blinker/wiper stalk needs to be from a wagon with the cruise on/off switch on the end of the blinkers)
  I don't remember seeing if the clock spring socket for cruise buttons was different (has radio controls on My steering wheel)  are they cruise specific? i bought a combination switch with clock spring from a cruise spec wagon.    What actually is needed?   1.Blinker stalk has the on/set switch so a combination stalk with wagon specific will be needed for mine unless it can be separated?(i got the correct one, i did wonder if i could "tap in" to the wiring further down the loom and just add a push button on/set on the dash etc... but messing with this more advanced electronics made me spend the extra on the correct blinker switch version)   2. Steering wheel control buttons (wheel back cover has cut outs for the buttons to poke through) depending on where you get your switches, you may need the steering backing with cut outs for the switches, although i did read you could do this yourself.. when fitting switches, don't tighten the screws too tight or you'll snap the brittle plastic mounts.. also need to be sure the covers are sitting perfect or the air bag will push on and break the switch holders also.    3. Brake switch on master cylinder, i was lucky the master was recently swapped to fix a brake issue and had this switch on it, but it may just fit into the existing master cylinder (not sure)   4 cable and vacuum motor assy (and tap a thread in rocker cover for cable bracket) this cable pull assy has the cruise control computer built into it i'm led to believe, it's worth checking the cable end to the throttle body isn't damaged if you are getting one from a wreck, i saw several broken ones at the wreckers due to people not unclipping them correctly. or cutting the cable even. i'll attempt to take photos when i install mine.    5.loom section that joins cable pull motor and brake switch that goes into the cabin under dash. there is a loom section to replace. you can be sure it's the one by unplugging the power steering switch wire, and following it up, to the brake switch on the master, and it also plugs into the wipers and the cruise control module.  this loom section has a grommet into the firewall above the accelerator pedal and is also plugged into the brake switch on the brake pedal and a big connector behind the fuse box. and some plug/s under the steering column (these are likely the steering wheel controls and on/off switch)  the big plug behind the fuse box has like a locking lever on it that you flip over and it can be unplugged, and the holder slides off a tab if needed (can't remember if i needed to do this, but i did it for access at minimum) then you can remove the loom section through the firewall hole by pushing the grommet from the engine bay and pushing the plugs though the hole one by one. (this replaces the existing one, as it has the wiper motor etc plugs in it plus the cruise plug)           Anything else?  Series 2 and 3 needed. Series one is different but is that just the control module or everything different? 
if your car doesn't have ABS, this could be a different thing to deal with, and also if it's manual (there could/should be a clutch switch, and maybe a neutral switch for the gearbox) you'll need to read further unless i come across it in my searches.    Thanks for any input and I'll update when I figure it out, but i am fairly sure this would just plug in and work from what i've read so far. 

Below are threads I've got this short list above from(I'll add pics later and confirm it works if so)






  some links that may be helpful from other forums (note Series 1 is different, but the process might be same)

https://fordforums.com.au/showthread.php?p=2490228

https://www.fordforums.com.au/showthread.php?t=11210865

this link is what google AI puts up as the answer to how to fit cruise to an AU. it's for EF/EL but may have some relevance. 
(basically follow the wire from the brake switch on the master cylinder and disconnect it from the donor car etc)
https://www.fordmods.com/ford-technical-document-cruise-control-d11#:~:text=The connector should be located,up behind the Fuse Block.

Sure enough checked my back brakes and one of the springs broke off. Gonna fix it tommorrow and flush the fluid and see if that makes it happy.

Have seen them run with coil wires reversed 

Pretty sure they do run like this. But not sure if there's any issues from it?

Thanks all, will the engine run if the coils wire arse about, seem to remember from trade school that of would but that was a long time ago, memory is a bit foggy now.  It's a six cylinder tacho so I think it might have been original, tried the trimpot  and other methods mentioned on here to change from 6 cyl to 8 but still doesn't work. Just trying to decide it it's a wiring issue or the tach. Guess I could always run a wire from the coil neg straight to the tacho and find out that way.

Usually means low fluid level, or the hydraulic spool inside the Master cyl has travelled too far in one direction hitting the switch. Check your brake system thoroughly first, may be a faulty switch.

Last night I was driving my xf when the brake fail light came on, it was coming on dimly and came and went a few times but has since disappeared. Ive heard that this light comes on when the proportioning valve moves too far one way but Im not too sure on what it actually means. The way it came on makes me think that its a dodgy switch but what else can I check to make sure everything is tip top.

Shims usually live behind the upper arm front mount I thought, used to increase caster, by pushing the top pivot point back?   The upper arm clamp, should self center on the ball joint recess, when fully tightened?   And yeah, lower ball joint wear caused excess toe/camber on my BF. It had been previously aligned to compensate, but when I fitted new ball joints, I didn't think to re-adjust. Note - After not adjusting the alignment, it wore the front tyres, within around 15,000km's. When later fitting new tyres, I located whiteout marks for the factory toe settings, and set to those points. Further confirmed, with a DIY string/tape measure arrangement.