Yesterday morning we decided to on a bit of retail therapy.  It was nice and sunny and as we walked out to our Karoq 1.0 TSI Tech DSG MY19 we were in good spirits, even though it was -3*C outside and the car was rather frosty.

 

On starting the engine, I noticed the ACC symbols weren't showing on the display behind the steering wheel.  By the time we got to the M25, temperature was above zero, but fiddling with the Cruise Control lever still wouldn't restore ACC, nor would it do so later as the outside warmed up a bit more, nearer destination.  So we had to drive along using the throttle pedal - it all felt rather crude and behind the times.  Anything going wrong like that tends to make me worry.

 

Now I think on, I'd started the engine before clearing the windows, so maybe ACC didn't like the frost over its windscreen sensor and so refused to work.

 

On returning to the car after spending far too much at John Lewis, I started the engine and the ACC symbols had thankfully returned to the dashboard, so I used ACC on the way home.  I do like ACC in spite of its few foibles.

 

The only other time I've had the ACC fail was doing 70 along the M4 in the rain - there was a 15min spell when it was really tipping it down and ACC disappeared and the car started to slow down.  I think it only came back after stopping off at the next services - this was 2-3 years ago so don't recall the exact sequence of events.  I assume the amount of water in front of the sensor was too much for it during the downpour.

 

All this points to a sensible safety feature, not a worrying fault as I had been thinking.  If the ACC windscreen sensor can't 'see' properly for any reason when travelling along, it turns off the ACC.  It won't even let it come on if starting the engine before clearing any frost, dirt leaf etc. in front of that sensor.  It only comes an again after stopping, clearing  that area of the windscreen if that is necessary and only then restarting.

 

Anyone else noticed this ACC behaviour and does my explanation sound right.

ACC doesnt use the windscreen sensor. There's a radar sensor in the front grille. I suspect a covering of frost was affecting the sensor, once the frost had thawed it was OK again

Ahhh, thanks for putting me right.  Same thing applies though - it's best to keep the sensor area clean and clear, I often wipe the 4 front emergency stop + parking sensors before setting off so must add the centre front grill to that.  Like I said, ACC only seems to reset after restarting the engine.

Strange, had similar with my non-ACC CC, it just wasn’t there when tried the switch.  Stopped, shut the car down fully then started up, then all was well with the world, CC was back.  Was -5c, might be a cause, might just be a ghost in the machine. 👍

Normal CC doesn't use any sensors though so maybe a software glitch resolved by the stop and restart

Surely it uses sensors or a camera as it adjusts speed when following a slower car.

Normal CC doesn't as it doesn't adjust the speed set

Edited 22 January, 20242 yr by sussamb

This has happend to us, but turning off the car and then restarting fixes the problem.

it is not a temp ralated problem, will be a software problem. not that they will say so.

I've found that the ACC tends to turn itself off when the battery is a little low, after running for a short while there is enough in the battery to turn it back on if you reset it by switching on and off. One problem I have found is the radar system does not like enclosed spaces, there are road works on the A14 near Stowmarket which has concrete walls either side for a couple of miles. The radar can loose the car in front so I have to turn the system off through the road works.

1 hour ago, sussamb said:

Normal CC doesn't as it doesn't adjust the speed set

My car does have ACC, but I have mine set as normal CC and it does slow when there is slower traffic in front.

Routemaster, I didn't know that you could turn off ACC and just run it as a normal cruise control, how did you manage to do that - not that I'd normally want to as I find ACC, although not perfect, is safer than just using on ordinary dumb CC and certainly makes for a more relaxing drive.  Anyway, it sounds to me like you still have ACC running, as surely slowing down so you don't crash into traffic in front, is it's main feature.

5 hours ago, Routemaster1461 said:

My car does have ACC, but I have mine set as normal CC and it does slow when there is slower traffic in front.

 

Ah well that doesn't happen in a car that just has normal CC.

On 20/01/2024 at 14:13, croquemonsieur said:

Yesterday morning we decided to on a bit of retail therapy.  It was nice and sunny and as we walked out to our Karoq 1.0 TSI Tech DSG MY19 we were in good spirits, even though it was -3*C outside and the car was rather frosty.

 

On starting the engine, I noticed the ACC symbols weren't showing on the display behind the steering wheel.  By the time we got to the M25, temperature was above zero, but fiddling with the Cruise Control lever still wouldn't restore ACC, nor would it do so later as the outside warmed up a bit more, nearer destination.  So we had to drive along using the throttle pedal - it all felt rather crude and behind the times.  Anything going wrong like that tends to make me worry.

 

Now I think on, I'd started the engine before clearing the windows, so maybe ACC didn't like the frost over its windscreen sensor and so refused to work.

 

On returning to the car after spending far too much at John Lewis, I started the engine and the ACC symbols had thankfully returned to the dashboard, so I used ACC on the way home.  I do like ACC in spite of its few foibles.

 

The only other time I've had the ACC fail was doing 70 along the M4 in the rain - there was a 15min spell when it was really tipping it down and ACC disappeared and the car started to slow down.  I think it only came back after stopping off at the next services - this was 2-3 years ago so don't recall the exact sequence of events.  I assume the amount of water in front of the sensor was too much for it during the downpour.

 

All this points to a sensible safety feature, not a worrying fault as I had been thinking.  If the ACC windscreen sensor can't 'see' properly for any reason when travelling along, it turns off the ACC.  It won't even let it come on if starting the engine before clearing any frost, dirt leaf etc. in front of that sensor.  It only comes an again after stopping, clearing  that area of the windscreen if that is necessary and only then restarting.

 

Anyone else noticed this ACC behaviour and does my explanation sound right.

I get a dashboard warning saying acc is impaired and not available  when it rains  heavily,  didn't notice any issues during  frost 

On 22/01/2024 at 17:06, sussamb said:

 

Ah well that doesn't happen in a car that just has normal CC.

 

This is the first car where I have had cruise that has operated like this.

On 22/01/2024 at 11:27, Routemaster1461 said:

My car does have ACC, but I have mine set as normal CC and it does slow when there is slower traffic in front.

 

If it slows itself down which is the whole point of ACC then why do you think your car is somehow only using normal cruise control?

16 minutes ago, SuperbTWM said:

 

If it slows itself down which is the whole point of ACC then why do you think your car is somehow only using normal cruise control?

 

Because ACC can do far more, controlling the speed to the speed limits. For instance, if you are on a 60mph road and there is a bend which the car thinks that you can go round at only 40mph, the car chatrges in at 60mph, then slams the  brakes on, then goes ound at an uncomfortably fast speed, then speeds up to 60mph again.

 

If you set the CC at , say 50mph on a 60 mph road and you go into  a 30mph limit, the car will charge in again, brake hard to 30mph, then when the limit goes back to 60mph, cruise resets to 60mph, not 50 mph.

 

I have managed to sety mine so that it stays at whet I set until I change it, so it is just like a normal cruise except it does slow down to the speed of the vehicle in front.

I think I understand now, basically you still have and use ACC, ACC cannot be turned off into dumb cruise control to many people’s disappointment ( when they don’t like ACC)

 

what you have done is turn off some other features that use traffic sign recognition for example which enhances the ACC experience by changing the speed setpoint. 
 

ACC in its basic form will never ever change the speed setpoint initially input on the dash but to call that normal cruise control isn’t quite right. 

Routemaster1461.  What you seem to have is ACC+, I thought it was actually called Predictive Cruise control, or something like that, can't remember, and there had been much criticsm in a thread some months ago (or was that years ago now) about the extra features, particularly about it slowing down too much in bends.  People were glad that you could at least switch it back to an ordinary ACC system.  However I can't now see anything other than ACC on the Karoq website, so maybe they now simply call the new system ACC, incorporating all the extra poorly implemented features that at least you can switch out.

 

Haloween1, as I noted before, my ACC (MY2019) has only failed once a couple of years ago for a short while, in very heavy rain.  The other failure to operate recently in freezing weather is the only time that this has happened to me in 4.5yrs, so not too worried my ACC is going wrong, anyway it does seem to fail safely.