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post #1 of 10 (permalink) Old 06-19-2017, 02:33 PM Thread Starter
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Question Adaptive Cruise Control (ACC) problem

I have a 2017 VW Alltrack SE. While ACC works well most of the time, I have one major issue with it that the dealer claims is a driver perception failure aka vehicle is operating as designed.

How to recreate this behavior
ACC is on I'm following a vehicle;
the vehicle in front of me slows to make either a right or left turn;
my vehicle automatically slows as expected
the vehicle in front of me completes their turn, clearing my path
my vehicle continues to slow down sometimes almost stopping for what seems like an eternity, but may be perhaps 3 seconds before it begins to accelerate.

My concern is someone is going to slam into the rear of my car since this is not the manner that most drivers react to a turning vehicle, they immediately accelerate when the road is cleared. I've learned to override this ACC behavior by stepping on the gas pedal when it occurs.

My Question. Has anyone else encountered this behavior on any VW with Adaptive Cruise Control.
Thank you
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post #2 of 10 (permalink) Old 06-21-2017, 03:50 AM
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post #3 of 10 (permalink) Old 06-30-2017, 08:49 PM
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I have noticed a bit of that with ACC, but not 3 seconds. I think you can simply step on the gas.

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post #4 of 10 (permalink) Old 06-30-2017, 09:36 PM
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Hi everyone!
I have a mysterious problem with my 2007 VW rabbit no one can seem to solve so far and hopeful you will have the answer! I know this is probably a long shot, but I'm desperate here, so I'm just gonna try it! Here it goes:

I live in LA, and I bought a 2007 VW Rabbit couple years ago. And it overheated a couple times when it's really hot out in the summer. The first overheating happened when I was on the way to Vegas, second time happened when I was driving in local street. Both times happened when the outdoor tempareture was really hot, between 96 to 106 F. Also, the AC wasn't working properly, it worked sometimes and sometimes it blew hot air. I was able to make it work by messing with the temperature control when it's not too hot outside. But on a hot day, the AC would simply not be cold enough even when it's "working." (It blew "cooler" air but not cold.)

I've been driving the car like this for a couple years and the overheating problem never came back after those two times. (The car was actually OK when I drove back from Vegas on that same trip. Of course I had the AC off on my way back.)
Just couple weeks ago as the weather got hot again this year, I thought I would go get my AC fixed at a local mechanic shop. And the mechanic changed out the AC compressor, and the two belts while at it. Now the AC is blowing cold air! BUT, the overheating problem came back!! So I took it back to the shop and the mechanic tried to figure out what's causing it by swapping things out in the cooling system one by one till everything has been swapped out. But nothing helped! He swapped out the thermostat, temperature gauge, O-ring, water pump (the water flow is normal and the two fans are working fine according to him), flushed the system while at it and whatever he could think of that could've caused the problem. He even did pressure test on the engine to see if it was the head gasket, and the result seemed normal.

After this first mechanic shop gave up. I took my car to another shop where they claim to have certified engineers for VW. I took my car there to see if it has an electrical issue. However, the computer read nothing except a code for a failed coolant sensor which they swapped out and still didn't help. While I though the overheating problem only happens when the AC is on, the shop told me they could get the car to overheat even with the AC on! Now the engineer there is suggesting me to let them look into the cooling system starting from the thermostat check up and I'll have to pay more for their labor of course which is not cheap. But If the thermostat wasn't it, he will have to keep looking and check on all the parts in the cooling system again! But I'm thinking, that's repeating what the first shop has done! The only difference will be this shop claims that their engineers are certified by VW.

So is there anything else anyone can think of that might've caused this mysterious overheating problem!? The dealer did recommended me a "Brake Vacuum Valve" replacement when I took my car in for an AC diagnose, but the first mechanic shop said it isn't leaking like crazy, so a replacement shouldn't be necessary. But i've read that leaking brake vacuum valve can cause overheating problem too.
Or the radiator being too dirty? Or is there a chance that the ignition power supply is acting funny? Or anything else at all!?

If anyone on here has any suggestions, you are more than welcome to chime in!!
Please help me out here! I'm really desperate!
Thanks a ton ahead of the time!


Last edited by Shawn Tseng; 06-30-2017 at 09:39 PM.
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post #5 of 10 (permalink) Old 06-30-2017, 11:13 PM
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Shawn, this thread is about adaptive cruise control, not air conditioning.

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post #6 of 10 (permalink) Old 07-13-2017, 12:58 PM
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post #7 of 10 (permalink) Old 07-25-2017, 02:20 PM
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I don't have ACC in any VW/Audi product but I do in my Volvo and it is not normal for it to take 3 seconds to notice the car you were following is no longer there and to start to get back to speed (at least in the Volvo and I would assume the VW should be similar).

There may be a slight lag but the Volvo ACC at least does a good job following and accelerating when no longer following. I'd bring it back to the dealer and say that that is not normal.
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post #8 of 10 (permalink) Old 11-21-2018, 11:25 AM
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Yes I have had that problem in my 2018 VW Passat. The ACC stopped working and had to take it in to the dealership and they had to recalibrate the sensors. I am hoping that this might also fix the problem of the car slowing when someone slows down when exiting to the lane to my right.
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post #9 of 10 (permalink) Old 12-21-2018, 12:11 PM
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I had the same issue with my 2017 Alltrack. I just assumed it was the sensor still sensing the car until the car moved out of line of sight, and of course, because I was still approaching, it would continue to brake more firmly. In other words, I can recognize the turn and know based on my speed that I don't need brake because the car is moving out of my way, the sensor only sees the car is there and the distance is closing.

That said, as someone else said, you can simply step on the gas.
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post #10 of 10 (permalink) Old 06-29-2019, 12:34 PM
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I have a very different problem. When adaptive cruise control is on and I’m fallowing behind a car in traffic and the car in front of me eventually stops. My vehicle stops approximately 20 feet away. If the vehicle in front of me switches lanes my VW atlas 2019 begins Excellerating even though there was another car immediately in front of the car that had switched lanes. I find I have to quickly slam on my brakes to avoid rear ending that Second vehicle. It has happened at least five times. I wonder if this is just my vehicle, because I’m sure someone else would’ve gotten into an accident with this already.
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