cruise control problem

my cruise control has never worked since i bought my disco. when the button is pressed you can hear a click in the passenger footwell and also a click when you press the - button but nothing from the + button, could this be a loose wire behind the airbag or something else, ive no idea how it works, any help would be great

most likely vacuum pipes... easy job... there are loads of posts about how and what to do...

ive been looking at the cruise today, all the rubber pipe ends had split, what i dont understand is, does the pipe which goes on the vaccum pump (under jack) go on the big nipple or small and where does the other end of this pipe go as it looks to have been chopped near the steeringwheel (within the engine bay). the actuator pipe appears to go through the bulkhead to the brake switch, is this correct, the actuator does work when you suck on this pipe so id have tought there mixed up or something. any help would be great thanks

from memory there are two small pipes that go between the small nipples on the pump and the output for the actuator goes on the big nipple..

yea there ok, what i need to know is the pipe which goes on the big nipple of the vaccuum pump, where does the other end of this pipe go to as it has been chopped near the bulkhead.

ok.. the pipe comes out of the pump to a t piece, from the t piece one pipe goes to the brake pedal switch and another goes to the actuator.... the one to the brake pedal switch is the one that breaks the vaccuum when you put your foot on the brake to dissengage cruise

ahh i thought it might work like that, funnily its got a straight connector half way on the pipe between the brake and the actuator so someones been messing before. thanks for your help

no worries.. let us know if you get it sorted... I replaced all my pipes with silicon washer jet hose from halfrauds - works great except the decrease speed button dissengages cruise.. but I can live with that

mjltigger said:

no worries.. let us know if you get it sorted... I replaced all my pipes with silicon washer jet hose from halfrauds - works great except the decrease speed button dissengages cruise.. but I can live with that

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No such thing as a decrease speed button, only disengage/re-engage so the RES switch is functioning correctly.

I agree with Discool, that's how the cruise works on mine. No decrease, switches the cruise off and when you pull it again the 'resume' function operates.

ok ive repaired all the split ends and fitted the 'tee' piece where it should be but still no joy, if i suck on the pipe at the pump end the engine revs which suggests its something electrical now, if i press the down button i hear a click under the passenger seat but nothing with the up button, could it be the swivel connector behind the steering wheel. also how can i check the pump works as it should only kick in over 30mph, cheers

OK, to test the pump you need a +ve and 2 -ve feeds, pull the pump out (again - sorry) and where the plug goes there are three terminals.. now I can't remember which one is which - I experimented with mine with no ill results but be careful, if you connect one +ve and one -ve to the correct pair of terminals the pump will run, when it is running apply a -ve feed to the third terminal and the pump will make a fairly decisive click (valve switching) - do this test with the pump detached from the rest of the cruise control

with the engine OFF and the plumbing all fitted, with just the single -ve you will get enough movement in the actuator to take up the slack but not enough to move it, this should then stay dead still without relaxing back until you release the power.

Applying the second -ve feed will make the pump move the actuator all the way (to full throttle) - this should be very quick so be ready to remove the power fast to prevent damage to the actuator.

Finally with only the single -ve attached pressing the brake pedal should make the actuator relax and let go the throttle.

If that all happens as it should then the issue is as you say electrical, either the cruise ecu or the rotary coupling on the steering wheel or the switch itself.

Just to let you know, the relay?? click when I press the - button is audible on mine but there is no audible click when I press + so the lack of it doesn't tell us much.. removing the rotary coupling look pretty simple but luckily mine passed all the tests above so I didn't have to do it..

discool said:

No such thing as a decrease speed button, only disengage/re-engage so the RES switch is functioning correctly.

Click to expand...

well that's cool cos that is how it works - resume works fine, just not how the owners manual says it should work.. oh well, not to worry and cheers for letting me know

mjltigger said:

well that's cool cos that is how it works - resume works fine, just not how the owners manual says it should work.. oh well, not to worry and cheers for letting me know

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In some ways it could be right, press the the RES switch, that disengages and without touching the throttle the vehicle will slowdown.

yeah it does lol.. but keeps on slowing down till it stops, from the manual I expected it to slow down a little each press like the accelerate button...

just got a day to myself so thought i'd tinker with the cruise again, all the pipes are ok and i checked the pump today, it does take up the slack when 1 -tive is added and pulls right in when a second -tive is added so alls well there, the fuse hasnt blow and you do hear a relay click when the decel button is pressed over 30mph, so that tells me the speed sensor works and theres power to the relay, my question is - is there a way to check the swivel steering wheel connector and the ecu without replacing, also is there a likely hood of chaffed wires anywhere as i havent hear it to be common on these. thanks i had though of gaffer taping my multimeter to the bonnet and putting the probes on the pump wires to see if theres power to the pump over 30mph but i diddnt know if theres a better way.

I've not played with cruise on a Disco but I do know the rotary coupler can pack up. On the Range Rover Classic, there is a fold in the ribbon cable and over time fatigue causes the tracks to break. I suspect the same is true on the Disco. The rotary coupler, or spiral cassette, is different on the Range Rover Classic, but the theory is the same. I also seem to think Disco ones are quite expensive but you can test the coupler but you have to remove it and then run continuity tests on each track. Fiddly, time consuming and often frustrating but if you can sort it, it is most satisfying.

ok i'll tyr that then, am i right in thinking the best way to take the steering wheel off is to disconnect battery and leave 20 mins before touching the airbag, never can be too safe with these things

would go for an hour if it was me just to be on the safe side lol...

i don't suppose popping all 4 wheels on axle stands would help?