Cruise Control drops out

[g0gcd]

Hi,
Newbie to forum but experienced in Galaxy, Sharan, Alhambra. This is my first Alhambra but 4th Shalaxy. It's a 2008, Alhambra 2.0TDi

Cruise control has been ultra reliable and very smooth in my previous cars. This SEAT is lumpy in comparison. The cruise control works for 4 to 16 miles from cold but then disengages and won't let me re-engage it. A simple ignition switch off and on doesn't reset it, it seems to need a wait.

VAG-COM reports all the switches behaving, whilst stationary. I haven't logged the drop out whilst I'm moving as yet, as I'm not sure what I'd be looking for.

I didn't like the look of the clutch switch; it seemed to be falling apart, so I replaced it anyway, with no change to the CC behaviour. I did discover that the acceleration surges in steps, most uncomfortably, whilst there was no clutch switch installed!

The brake lights are conventional bulbs and have been swapped for new, just in case, with no change. Brake lights seem to be working correctly.

The dash indicator remains on all the time that the CCS is switched on and as I mostly drive motorway, that's all the time.

I can't see any intermittency in the stalk but I'm going to try the switch cleaner approach next, just to see if that's any different.

The only other thing is that there is an old fault showing up regarding the camshaft sensor (no output). The car seems to be driving ok and there's no dash warning light but could this be telling the CCS to drop out? Would it make sense to fix this fault first before moving on to trying to fix the Cruise?

Thoughts please

John

Additional info - I am aware of the potential stalk issue. I've tried the cruise control whilst either right and left turn or left turn indicator is selected and can't get it to engage. As it seems to be reset only when the car has sat for a while, I'm steered towards it being engine temperature related and thinking that the sensor change might be a good idea... It's not cabin temperature related as I've run with the aircon on freezing but it didn't extend the time that it worked...

Yet more - managed to drive with VAGCOM connected and brake/clutch/control switched all working as expected. For the third time, I noted that, after it has dropped out, if I just cruise on using the accelerator to pick up and don't touch the brake/clutch then it may switch back on again. Boy, is that frightening! I think that means that when it cuts out, it isn't being instructed to, it just loses the capability to control the 'throttle'.
I didn't notice anything in the VAGCOM data, apart from the sudden drop in power resulting from the CCS dropping out. The timing shifted back to zero but whether that was cause or effect, I don't know. It's annoying but the VAGCOM I have loses connection with the ECU after a couple of minutes, so I haven't been able to get any more snapshots. Any ideas?

[glowplug]

Perhaps stating the obvious but it would seem that you have an electrical connection issue somewhere in the wiring loom. Why not get the wiring diagram and do a methodical circuit trace. This is perhaps why the VAGCOm is not detecting anything. The fact that your VAGCOM is dropping out as well could further point to connectivity issues. Could also be the actual ECM as I believe the CC is built in rather than using a separate CC system. Failing all of that you could install an after market one. I have done so on a number of cars in the past.

e.g.

Aftermarket Cruise Control Kit from Bridgwater Electronics (http://www.bridgwater-electronics.co.uk/cruise-control-kits/c51)

also see

Cruise Control Not Working - TDIClub Forums (http://forums.tdiclub.com/showthread.php?t=365328)

[g0gcd]

Thanks Glowplug, for those useful steers. I also contacted the supplier of my VAG-Com and he admitted that they'd had a bad batch of leads, so I've had to wait a while until a new one arrived.

The problem had become predictable and interestingly (really?), it showed that I got further in the cold weather before the drop out. This only made me more sure that we had a temperature related problem in the engine bay, probably wiring. This morning, I disconnected the Camshaft Position Sensor before starting and got no Cruise for the first two miles. Before the car had warmed up, I stopped and reconnected the sensor and the Cruise worked. I have finally established a link between the sensor and the cruise control.

So next, I'll be following your advice and checking through the sensor wiring. There's nothing obvious at the camshaft end (it won't be obvious, will it?) so I'll trace it through to the controller. I hope that it isn't the controller itself - but if it is, it will only be a bad solder joint and I can tackle that.

I had ordered a replacement sensor anyway - I can't find any information about how to change it. I will start another thread about that.

So thanks and, should anybody want to know, YES the Camshaft Sensor can cause the Cruise Control to drop out (and re-engage!).

John

EDIT - PS At least there has been some benefit to being trained as an electrical engineer....
I am now pretty confident that the wiring from the engine mounted sensor connector is ok back to the ECU and that the sensor is faulty.
I'm also confident that this little beast is responsible to knocking my Cruise Control out of engagement, although not properly because it can re-engage itself, when it has the mind to. .....
SO - ebay sensor on order and I'm trying to find out how to change it. There doesn't seem to be a YouTube to make it easy for me, so perhaps I'll do one whilst playing.

When I have replaced the sensor and confirmed my theories, I'll come back and properly close this thread with the findings. Meanwhile I'm looking for help on how to change it (another thread running on that!)

Note: No MIL indication - that's not right, surely?

EDIT: Old sensor started to work properly/consistently whilst off the car. Having now re-installed it, not only does the car start properly, the cruise control now works properly too. Now I just wait for it to break again.
Cam shaft sensor DOES cause Cruise Control to drop out (and sometimes re-engage!)
Faulty can shaft sensor DOES NOT cause MIL indication, just poor starting (and improved fuel economy!)
I hope that my notes are useful to someone.