Voltage Stabiliser location?

[davegsm82]

Anyone know the aproximate location of the voltage stabiliser unit on the MK7? Have seen someone suggest it's in one of the wheel arches, which could be possble but I think it unlikely.

I'm having problems with my ACC Front assist and Start-stop, which usually points to a dead battery, however I've replaced and correctly coded the battery and the fault I'm having seems to be persistent when it's rained so I'm suspecting water ingress.

Have attached a picture of the unit I'm looking for.

 

[jimlloyd40]

I would suggest finding out exactly what's wrong before you buy parts you can't return if it doesn't fix the problem.

 

[davegsm82]

I would suggest finding out exactly what's wrong before you buy parts you can't return if it doesn't fix the problem.

Yea, thanks for that, really helpful.

As it happens I'm an electronics engineer and actually locating the module so that I can inspect and test it would be really useful, a bit of a heads-up on the location would be nice but I guess I'll just use my eyes and spend ages tearing the car apart instead.

 

[ryansonfire]

Yea, thanks for that, really helpful.

As it happens I'm an electronics engineer and actually locating the module so that I can inspect and test it would be really useful, a bit of a heads-up on the location would be nice but I guess I'll just use my eyes and spend ages tearing the car apart instead.

I heard they used to put a filtering cap on the output of the alternator but I don't think they do that anymore. Here is how they wire the gen 3. The battery is the voltage "stabilizer". The voltage regulator is built into the alternator and i have yet to see these fail. "B is the batter, "c" is the generator and "c1" is the regulator.

 

[davegsm82]

I heard they used to put a filtering cap on the output of the alternator but I don't think they do that anymore. Here is how they wire the gen 3. The battery is the voltage "stabilizer". The voltage regulator is built into the alternator and i have yet to see these fail. "B is the batter, "c" is the generator and "c1" is the regulator.

Thanks for that ryansonfire, in guessing the voltage regulator is directly controlled by the can gateway, rather than being self contained like they used to be.

I checked the coding of the battery again and everything looked good there, however when I checked the ACC radar it had no communication at all, rather than being just intermittent like it used to be. After I ran the engine for a while and it warmed up it started communicating again.

Do you have access to the wiring diagram for everything between the can gateway and the radar? As far as I understand the front facing camera would also be connected to that bus, but I don't have the leave assist camera.

Regards, Dave.

 

[ryansonfire]

Thanks for that ryansonfire, in guessing the voltage regulator is directly controlled by the can gateway, rather than being self contained like they used to be.

I checked the coding of the battery again and everything looked good there, however when I checked the ACC radar it had no communication at all, rather than being just intermittent like it used to be. After I ran the engine for a while and it warmed up it started communicating again.

Do you have access to the wiring diagram for everything between the can gateway and the radar? As far as I understand the front facing camera would also be connected to that bus, but I don't have the leave assist camera.

Regards, Dave.

I work at an Audi dealership, so it would be for an a3. I'll see what I can find tho

 

[ryansonfire]

The first two are the whole thing with the identifiers and the last two are close ups with the pin number

 

[davegsm82]

The first two are the whole thing with the identifiers and the last two are close ups with the pin number

That's great, thanks, confirms my thoughts that there's no other units connected to that canbus.

That does mean unfortunately that if the radar itself is ok, then there's possibly something up with my can gateway. If that's the case then I've no idea where to start because apparently the can interface takes care of the component protection and I'd very much like to not get involved with that mess.

 

[ryansonfire]

Honestly, Ive replaced a few of those acc cameras but never had the issues with the master or gateway on this platform.

 

[davegsm82]

Honestly, Ive replaced a few of those acc cameras but never had the issues with the master or gateway on this platform.

Sorry for the confusion, by 'master' do you mean the radar unit? My radar unit is the early one with the domed front, supposedly that one doesn't have component protection, model 5Q0907541G.

Is there any risk with plugging in a used can gateway and simply configuring it to have the same installed components and battery parameters?

 

[ryansonfire]

I was saying "master" because on a lin bus there is a slave and master. I would assume the camera is the slave and the control module is the master, but without looking it up I have no idea what bus it uses. The gateway is just the interpreter for the different buses to communicate to. I don't know if I've personally ever seen a gateway fail.

 

[davegsm82]

I was saying "master" because on a lin bus there is a slave and master. I would assume the camera is the slave and the control module is the master, but without looking it up I have no idea what bus it uses. The gateway is just the interpreter for the different buses to communicate to. I don't know if I've personally ever seen a gateway fail.

Ah, gotcha. Ok, so on this system they communicate on 500Kbps CANBUS, the gateway is technically master and the ACC Radar and lane assist camera are both **Technically** slave modules.

I'm slightly grasping at straws suggesting the gateway, as you said it's really just the interpereter to help all the modules talk to each other, which is also why I think it could be failing. Because several of the other modules are reporting missing messages and several times today after turning the key, seeing the intermittent "Start-stop" and "ACC Unavailable" messages, I have tried to communicate with the ACC Radar (module 13) and it's had zero communications.

I have a CANBUS monitor which I'm going to try and plug in tomorrow to see if when the radar isn't talking, if it's just the Gateway can't hear it, or if it's actually just sitting there mute.

 

[ryansonfire]

Just out of curiosity, what faults are you getting?

 

[davegsm82]

Just out of curiosity, what faults are you getting?

Ok, so, take today as an example.

Get into the car and turn on the ignition, cluster displays "Start-Stop" and "ACC Front assist not available" after a couple of seconds.
Plug in VCDS and interrogate module 13 (ACC Radar) - No communication.
Interrogate the CAN Gateway and there's faults logged for no comminucation with the Radar, as well as other modules also complaing about lack of communication with the Radar, below is an example from module 10 - Park/steer assist.

1 Fault Found:
13637426 - Databus
          U1123 00 [008] - Received Error Message
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 2
                    Reset counter: 11
                    Mileage: 271614 km
                    Date: 2021.06.27
                    Time: 00:03:12

After stopping and starting the car (running a few errands, so driving half/a mile stopping/starting manually a few times) the ACC Radar and Start/Stop suddenly starts working again all on it's own.

Previously if I pressed the button on the stalk and tried to turn it on, it just displays "ACC Front Assist not available".

ALSO; All of this seems to happen particularly when it's been raining. Today it wouldn't work until I'd driven a few miles with 3-4 start/stop cycles. When it's dry, it works as soon as you turn the key MOST of the time, failing maybe once every 7-8 starts.

I replaced the battery about 6 month ago, checked the battery voltage, checked all terminals, fuses etc. CAN Gateway reports that battery is healthy, generator demand voltage matches actual output voltage etc.

 

[IWMTom]

Not unusual for these old dome radars to suffer from water ingress and fail.