fcd

Hello,

I was wondering if anyone with ACC has experienced this. I noticed my ACC would be down during cold weather and during warmer days would be active. We had an unseasonably warm day yesterday in the east coast and it was working fine. Today it was back in the 30s and it wouldn't work. By the way, I don't get any error message in the dash such as "ACC not working."

Where in the system would the problem be and how to fix it (is it a matter of insulating the wires? ) I do have some holes in my underbelly panels by my front doors due to winter weather driving, not sure if the ACC wires go through there. Thanks in advance!

goodoldsequoia

Any salt/dirt covering sensor?

fcd

Thanks for replying. The sensors are the 2 dome things on each side of the front bumper, where in other cars it would be fog lamps? Yes I've cleaned them before and it still wouldn't work. We did get some snow yesterday so I will try cleaning them again.

goodoldsequoia

ACC uses more sensors than the ones on front bumper, try to clean every sensor which looks a like a coin size, on both sides and rear. Any one sensor blocked, it "refused" to do ACC for you. Can you provide a pic of underbelly panel? I don't think anything inside the car will prevent the ACC from working properly though.

fcd

I tried cleaning the proximity/parking sensors if that's what you meant. Still no luck. I am attaching a pix of the right front passenger side panel that I mentioned that's has a rip on it. Do the wires pass over this panel? I'm guessing it must be a complicated network of wires for the ACC. How's everyone else's ACC holding up especially owners of 2012 A6s? Thanks in advance for any help and guidance on this issue.

goodoldsequoia

Never looked at what's behind that panel but I will say very unlikely wires went through there.
Are you sure the ACC problem is ONLY related to weather/temperature?

das2.7t

So, I have a MY 2012 and one of my two sensors has failed and rendered ACC inoperable. Even though there will not be a message telling you so, if you use VagCom, you'll see the errors there. It'll even tell you which is the offending sensor.

I tried all the obvious things (cleaning the dome sensor, cleaning and reseating the connector, giving it a light tap or two) but it still does not work. The unit operated and failed intermittently for around 4 months before finally failing permanently but my experience was opposite of yours. Only on long drives (2+ hours) would it fail when engine temps had saturated the entire front of the vehicle with warmth.

I'll be taking the sealed unit out this weekend and opening it to see if I notice anything obvious (like a failed seal) or any corrosion. I'll bathe the internals in electrical cleaner, let it dry out and then try again. This is a last-gasp effort, of course as the sealed unit is not user serviceable. A new replacement is over $4K and used units are less but risky. And, then, you have to take it to the dealer to have it coded to your vehicle (yes, it's a coded part) and then calibrated. It will not work otherwise and I have yet to find an indy shop that has the tooling to do it.

I'll let you know how it goes here next week sometime.

Edited to add: temp fluctuations are a common early instigator of electrical component failure. The heating and cooling expands and contracts the various circuit board materials and bi-metallics at different rates causing cracks and separations at the component level. Typically, when you see temp-related intermittent failures like this, it is signaling the death-throws of the device.

goodoldsequoia

Good luck , man. Wish you luck and update us here. I know I will be there not too many years from now even though it's 2021. It didn't work right from day 1.
What a German engineering...
I thought German is only not good at software stuff but I was so wrong. My 2021 gas pump seal broken at 7 months by itself, no crash or bump to the car, garage kept. Only 1600 miles!!

das2.7t

German engineering typically is indeed quite good. I've found that 21st century cars are like most other things these days; if something is going to break, it'll be in the first 5% of it's life or it will be fine through the expected life once you get past that normal "breaking in" period. For example, just because your pump seal failed during break in, it's not likely that you'll continue to have tons of problems as you move from that phase of ownership.

I can't feel bad about this radar sensor failing. My car was a first gen 2012 C7, picked up in October 2011 and it has 160,000 miles on it. I mentioned elsewhere on these forums that my total outlay for repairs that were not maintenance or normal wear-and-tear (like brakes or filters) was less than $4k for the life of the car. $4k for 10 1/3 years. It's been spectacular.

fcd

That's what I noticed although I definitely can't say with 100 percent certainty. I just noticed it was working right up until December when it started to get cold.. And when we had fluctuations in temp over the past 3 months it would usually work although not every time when it gets warmer than usual. It did work again this week as we had 2 days where we had unseasonably warmer weather (50s). I guess car's just getting really old. lol. Thanks again I was hoping that it was just something where i need to cover something or insulate the wires. But I guess it may be complicated to trace where the issue is and would probably need help from the dealership unless someone else has a similar issue and hopefully a not too complicated repair.