Cruise Control not working - UPDATE

[MickG]

Set up: I have a manual TD5 Disco 2 with 4.11 diff gears and run 265/75R16 tyres. I have recently had a True Speed speedo correction unit fitted through the SLABS to bring the speedo back in line.

Problem: My cruise control stopped working when I fitted the diff gears and has never worked since. I believe it may be something to do with the BCU but would appreciate anyone's input before I go back to my mechanic.

Aye, Mick

[Slunnie]

G'day Mick,

Retune the speedo correction unit to suit the diff ratios, not the tyre diameters and it should bring the CC back on. It'll probably be out by only a couple of km/h. The D2 reads the speeds from the ABS sensors and with the manual CC it needs to have this in sync with what it expects the driveline to be.

[MickG]

Originally posted by Slunnie
G'day Mick,

Retune the speedo correction unit to suit the diff ratios, not the tyre diameters and it should bring the CC back on. It'll probably be out by only a couple of km/h. The D2 reads the speeds from the ABS sensors and with the manual CC it needs to have this in sync with what it expects the driveline to be.

Thanks Slunnie

A dumb question perhaps, but I have just checked on my RAVE cd for the correct old diff ratio and it states 3.538:1, however on the True Speed chart 3.55 seems to be the closest to that figure? Short of trying it, if i go with the 3.55 on the chart will this suffice? Mine is a '99 series 2 if that helps.
Appreciate your input again.

Mick

[MickG]

At the risk of asking simple questions and frustrating everyone, can anyone explain why the following might be happening.

Background: Fitted my True Speed correction unit and it seemed the speed was about right although the cruise control still didn't function. So, back to the instructions and this time I reset the unit and set the unit again going off the new diff gears chart - 3.55 old and 4.11 new which stated 12.5 turns of the key. This has fixed the cruise control but now the speedo is definitely way out and the car is very jumpy - not sure if this is related?

Appreciate any help, Mick

[disconut]

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I dont pretend to understand this, but it sounds like it is fitted in the wrong place. Would it not go between the speedo sender (pulse unit), and the speedo head at the speedo. Sounds like it is screwing up the slabs unit by altering the pulses into it when it should only change the pulses for correction into the speedo unit. I could be way off beam here, but, just my thoughts.

Trev.

[abaddonxi]

Here's the trick.

You need a GPS and a pile of different coloured permanent markers.

Take out all the compensator thingys.

Get on the highway and once the GPS tells you that you're at the right speed put a mark on the speedo in the right colour. Do the same for 50, 60, 80,100.

Go home, switch to the monster muddies, back on the highway, change colours and do it all again.

Rinse and repeat.

You'll end up with a rainbow of coloured stripes on your speedo, and you'll need to make up a laminated colour chart to interpret it, but you won't have to worry about what speed you're doing.








That is until the muddies wear down and you have to do it all again.

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Cheers

Simon

[Slunnie]

Mick, I'm not sure why the speedo is so far out, though it will be out to a certain degree. The 4.11's will correct a 33 back to standard, though it will be a little out for a 32/31.7 etc. It should be by a few km/h, perhaps 5??? Whats happening when you say the truck is jumpy? I'm wondering if the speedo correction is just ever so slightly off the mark???

Disconut, in the D2 the SLABS computer reads from the ABS sensors the wheel speed (not the road speed). It then combines all of this and produces an output frequency that drives the other systems in the car such as the auto, ACE, CC, speedo etc. The SLABS computer is in essence the pulse unit, with the speedo correction happening on the output side. The CC needs the drivetrain to run at the correct speed as to what it expects in the manual otherwise it disconnects the CC. I assume its a safety backup, which is why the speedo correction is after the SLABS and not on the back of the speedo.

[disconut]

Hi Slunnie,

If its on the output side from the SLABS to the speedo then it should work?
Do other owners here have them fitted? Im curious.

Trev.

[Slunnie]

Yep, all in the same location. There is 1 fella that I know of in the UK who has the exact same setup as Mick, and it all seems to be working ok. (ie TD5 Manual 4.11's Truspeed). There has been 1 faulty unit that I know of that has been found in Aus also from a Melbournite I think it was.

[MickG]

Originally posted by Slunnie
Mick, I'm not sure why the speedo is so far out, though it will be out to a certain degree. The 4.11's will correct a 33 back to standard, though it will be a little out for a 32/31.7 etc. It should be by a few km/h, perhaps 5??? Whats happening when you say the truck is jumpy? I'm wondering if the speedo correction is just ever so slightly off the mark???

Problem not totally solved but I think I am close. Turns out the way the intructions are written has confused me 8O . A section states "only calibrate using the following method if you have changed tyres and diff gears" and there is a chart below this statement. Turns out this statement refers to the chart on the next page :roll:

Anyway, did my maths to work out % change for tyres and gears and plugged the necessary turns into the unit - 12.5 8) . Cruise now works and I reckon I am now between 5-10% out. I don't have a GPS so I will be recruiting someone at work tomorrow to drive at pre determined speeds and try and work it out from there. My only worry is I loose the cruise again as at 10% out, this means 2.5 (edit) rotations in this unit and that's got to throw something out. Will keep you posted and thanks for the input again......I hate car electrics and it's frustrating not knowing enough about them whilst trying to solve a problem :oops: .

P.S. If this doesn't work then the marker pens are coming out :!:

Slunnie, my truck was jumpy off the mark and seemed to drop out when pulling off plus it was rough and bouncy when coming off the gas. I put this down to completely the wrong info being sent to all the sensors due to one system thinking the truck was going faster than it was etc. As you can see I know next to nothing about how it all works and am having to learn the hard way but after I have re-set it again (even though I am still out slightly) it seems a lot smoother.
By the way, not sure if you remember Slunnie that I was getting large plumes of smoke when accelerating from around 1800 - 2100 rpm, well since the True Speed has gone in this has stopped. Still a bit of smoke but not a huge plume like before......embarrasing around town :oops: Again I would put this down to incorrect signals internally, any thoughts or am I way off the mark?

Aye, as always, Mick

[loanrangie]

Have you removed the brick from the pedal ?

[MickG]

Okay, I think I have solved my problem - well my speedo one anyway!! Turns out that the unit was claibrated slightly off the mark, so now I reckon I have got the speed reading pretty much right - give or take a few k's) and the cruise now works alongside style_emoticons/<#EMO_DIR#>/laugh.gif style_emoticons/<#EMO_DIR#>/laugh.gif style_emoticons/<#EMO_DIR#>/laugh.gif style_emoticons/<#EMO_DIR#>/laugh.gif
Going off the chart settings though, my speedo was ready 49kph when travelling at 60kph 8O 4.5 reverse turns later and I think I am pretty much there.

Another annoying fiddly thing ticked off my list of things to fix, next issue is trying to shoehorn my storage drawers into the back now that I have a cargo barrier fitted......the joys of bolting things to a disco style_emoticons/<#EMO_DIR#>/biggrin.gif

Thanks for all the input and until my next problem - which will be soon i'm sure, aye, Mick.

[Slunnie]

Hey thats good news Mick. Fixing the exhaust smoke was a suprise also, a pleasant one at that.

[MickG]

Originally posted by Slunnie
Fixing the exhaust smoke was a suprise also, a pleasant one at that.

Yeah, not sure why that was but at least it is sorted......for now anyway.

Aye, Mick