Cruise Control not working

Just got a 300tdi. The cruise control doesn't seem to work however it could be the way I'm trying to operate it as I don't have a user manual. Can someone enlighten me please on how it's meant to operate, the sequence of button pressing?

From the handbook ...

Press the cruise switch on the fascia just below the hazard light switch. Accelerate to required speed which must be above 28mph then press Set button on either the steering column or steering wheel, depends on model.

You can use the accelerator to increase speed, but when you take your foot off it should return to the set cruise speed.

If you want a lower speed, use the res button to reduce speed then press set when the speed is reached.

To increase speed, press and hold set, which will accelerate the car, and release set when new speed is reached. Or tap set repeatedly to increse speed in increments, 5 taps to 5 mph.

To disengage cruise, press the brake or clutch. The set speed memory will be cancelled when the master cruise switch is off or starter switch turned off.

Thanks Paul .

I thought it was something like that and I had tried it already. Just been out again too make sure, doing everything you described.



After pressing the cruise switch on the fascia just below the hazard light switch, the red light illuminates which suggests there's power to the system.

Can anyone talk me through some fault finding with cruise control?
Is there a common fault with them that I should be looking for?

There are known issues with the vacuum hoses it uses to maintain speed. I don't have cruise myself so can't point to the actual hoses, but that's where I'd start, check them all for kinks and splits.

As Paul D above, this is what the hose looks like at the T piece I cut the split ends off then put a few laps of pvc electrical tape around the end to stop it happening again. Diesel engine may be different.

One of mi mates as got a p reg 300tdi. Used to have a problem with his, if i remember right think it was just a problem with the set button on the steering wheel. He just poped button out, easy fix apparently.

If they're on the wheel (not on the separate pod) try popping off the front of the button with a small screwdriver from the top, you can then see the actual button and try pressing that...

My issues were a broken piece of the cover wedged in the gap!

Thanks for all the replies so far . I have checked the hoses and made some repairs as per Discool's recomendations. I have traced the hose that runs across the bulk head down to somewhere close to the airfilter where it's just lying around .

Should it be like that or should it connect to something?

GTSX said:

Thanks for all the replies so far . I have checked the hoses and made some repairs as per Discool's recomendations. I have traced the hose that runs across the bulk head down to somewhere close to the airfilter where it's just lying around .

Should it be like that or should it connect to something?

Click to expand...

I assume it's the same as a petrol engine disco if so then u have a small vacuum pump located under the jack. remove the jack and put your hand the hole below and concealed under the metal work is the pump, u may need a mirror to see it and that's where the hose goes to.

The jack is missing but I know where you mean. Just under the wheel chock (which is there) there's a small valve of some sort.
There are 2 small pipes attached one goes towards the turbo and one goes to the top of the airfilter. Then there are some wires a single wire and several going into a multi socket. I don't think this is what you mean though as there's no where for this vacuum hose to attache.

Are there any photos that anyone has please?

GTSX said:

The jack is missing but I know where you mean. Just under the wheel chock (which is there) there's a small valve of some sort.
There are 2 small pipes attached one goes towards the turbo and one goes to the top of the airfilter. Then there are some wires a single wire and several going into a multi socket. I don't think this is what you mean though as there's no where for this vacuum hose to attache.

Are there any photos that anyone has please?

Click to expand...

I think the one you are looking at is the EGR solenoid valve mounted on teh side of the wing. It should have three connections 1) vacuum feed from T-piece on main braking servo vacuum pipe, 2) connection to EGR diaphram and 3) vent to teh air filter box.

The cruise control pump/solenoid valve unit is under the jack panel and not visible.

To remove the cruise pump, get underneath the front and look up to where the pump should be. You will see three rubber feet/grommets sticking through the metal panel. Push them in to release the pump, which you can then pull out from top side. The rubber hose connects to one of the two stubs on the pump. One of the stubs is the air inlet and one the vacuum stub (which you need to connect to), but I can't remember how you tell!

Cheers

discool said:

I assume it's the same as a petrol engine disco if so then u have a small vacuum pump located under the jack. remove the jack and put your hand the hole below and concealed under the metal work is the pump, u may need a mirror to see it and that's where the hose goes to.

Click to expand...

Have posted couple of photos in Discovery Gallery showing hose arrangement on pump and throttle servo unit - however appears that the TDi has a different set up to that of the V8i.