Problem with internal lights on 2005 A4

[Themadsinger]

I have a 2005 A4 which has a problem with the internal lights - most of the time they will not work (that includes the front and rear internal lights, the glove box lights and the boot light. When the engine is running, if you toggle the switch on and off a coupld of times they will come on and if you keep at least one on, they will stay on even if you switch the main switch off and on again. When the engine is not running, that will not work and they will not come on. Nor do they come on when you open the door or remotely unlock it. I have checked and swapped the fuse and it did not help.

The only other thing I would mention is that I had an extra 12V feed off of the light in the glove box with a switch on the earth side to toggle on and off. That switch also acted on the negative side for another feed off of the cigarette lighter circuit. I noticed that when the light was not working and the toggle was switched off, the circuit for the ciggy feed circuit was on, sugesting that there was an earth leak back through the light circuit. When the lights are on, that circuit cts off.

Anyone have any suggestions what and where the problem might be?

[toff]

Hi,

Just trying to get my head round the second paragraph..

How come you've put a switch in the glovebox? Are you using the power from the lighting circuit (i.e. the light in the glovebox) to power an MP3 player / CD changer etc?

Al.

[Themadsinger]

Hi,


How come you've put a switch in the glovebox? Are you using the power from the lighting circuit (i.e. the light in the glovebox) to power an MP3 player / CD changer etc?

Al.

To power a bluetooth GPS receiver that I located in the glvoe box with the aerial up onto the dash, so I took a feed from the light in the glove box on the basis that I would never need power to the GPS when the ignition was not one.

The installation or removal of this (I have taken it off now as I have a tomtom stand alone unit) in no way coincided with the problem starting

[toff]

Hmm..

So was the switch a DPDT? Have you removed that completely or is it still in-line for the cig lighter circuit?

Al.

[Themadsinger]

Hmm..

So was the switch a DPDT? Have you removed that completely or is it still in-line for the cig lighter circuit?

Al.

I am not sure what a DPDT is. It was a simple toggle switch. I took a feed from the live side of the supply to the glove box light using a scotcj lock and then fed the negative line for the supply for the gps to earth via a switch so I could switch it on and off (mounted the switch in one of the blank button spaces above the stereo). Later, I put a feed for a cigarette ligther mobile phone supply on the drive's side of the car which I did by picking up a feed from the back of the fuse box for the cigarette lighther supply, wiring in an in line cigarette lighter socket and then connecting the negative to earth, again via the same switch. The switch was on the neative side of the circuit in both cases. The switch is still there for the phone supply but the supply for the gos has been completely removed and the wire for that supply dis-connected from the switch.

As I already said, when the set up was there with both connected, everything was fine, certainly to start with (I cannot recall exactly when the problem started since I only noticed it when I was using the car in the dark more with the darker evenings).

Do you want me to draw and up a circuit diagram? (although I am not sure why it would be needed)

Thanks

[toff]

Hi,

DPDT stands for Double Pole, Double Throw; meaning that the same switch can switch two independent circuits.

http://myweb.tiscali.co.uk/nuukspot/decdun/gc/dpdt.l.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/DPDT-symbol.svg/330px-DPDT-symbol.svg.png

Sometimes the legs on the switch can be so close together that a single strand of rouge wire (intermittently bridging the legs of the switch) can cause electrical glitches! Anyhow, doesn't sound like you're using one of those.

When a problem occurs on an A4, you'll usually find a fair few other people who've had the same problem (common faults). I haven't read any other posts where someone else has similar symptoms to you. There are one or two with regards to the magnetic door-closed / open sensor going wrong, but I don't think this is the issue in your case.

To me, it points to something that you've done by tapping-into the lighting / cig wiring looms :blackeye: sorry mate!

Does the problem occur regardless of whether or not you've got your mobile charger plugged in?

Does the in-line cigarette socket you fitted just have + and - or does it have a connection for illumination too?

Al.

[Themadsinger]

No, it was not a DPDT switch. Since both ends were connected to earth there seemed to be no issue (and I can still not see how this could have raised an issue, since everything is common on earth side!!)

The problem is complete independent of the position of the sitch and also whether the pone charger is plugged in. Indeed, since removing the GPS unit the lighting ciruit is no longer connected to the switch and hence the phone charger is complete independent of the lighting ciruict (except, of course, that they have a common earth somewhere!)

I think this discussion is maybe getting off the point a bit. I mentioned the additional wiring in the first post because of the fact that it was clear that there was some link to earth back through the lighting circuit as part of the problem and thought this might help with the diagnosis. Is there some main control module for the internal lights. Also, does anyone have a note of whatconnections go through the main internal light module above the gear stick in the roof as I am trying to identify where the problem might be.

Thanks

[Alan02]

Trying to suss your explanation,but it sounds like the switch you fitted is the Earth for the other circuits,so,when you turn it OFF the power is looking for the next easiest route to earth.

[Themadsinger]

Rrriiighhtt, even if that were the case before (which I don'tt think it would be as why would the "reverse earth" as I will call it only occur when the lights were not working - togglinh the switch to get them on would stop the power to the mobile charger if the switch was in the off position), it cannot be now as the switch is, as I said in my last post, now completely isolated from the lighting circuit.

If it moves us on, then fine what I did caused the problem, but what is the problem since it is clearly now arising somewhere else, which leads me back to my previous question - is there some central controller for the internal lighting which might be causing the fault (whether because of what I did or otherwise).

[bez101]

Rrriiighhtt, even if that were the case before (which I don'tt think it would be as why would the "reverse earth" as I will call it only occur when the lights were not working - togglinh the switch to get them on would stop the power to the mobile charger if the switch was in the off position), it cannot be now as the switch is, as I said in my last post, now completely isolated from the lighting circuit.

If it moves us on, then fine what I did caused the problem, but what is the problem since it is clearly now arising somewhere else, which leads me back to my previous question - is there some central controller for the internal lighting which might be causing the fault (whether because of what I did or otherwise).


HAHA:biglaugh::aargh4: this is geting funny i think you need to chill an call a sparky :rocketwho

[Themadsinger]

No fine, I was hoping someone here might be able to assist but it seems not so I shall try elsewhere.

I am perfectly calm but it seemed that the responses I was getting were concentrating on a seemingly irrelevant point. I seems to have, at my first try, asked something the answer to which is beyond the abilities of those here. Never mind. I will remain in the dark for now (sorry for the punn - I could not resist)

[B8 TDI]

So what you are saying is that you screwed up your cars electrics by treating a highly sophisticated electrical system as if it is a toaster, and now you're ****** with this forum because no-one here has clicked thier fingers and magically fixed it for you?

Phone a sparky, pay the bill, and write it off as a learning experience.

PS: I'm sure you'll be just as welcome in any other forum as you are here.

[bez101]

as above you beat me to it if you dont know what your doin pay but ppl on this forum do know whats what there all very helpful as we come across problems with out cars and get them fixed we share the info
maybe when you have got your self inflicted wireing prob sorted you could share then maybe you stop 1 or 2 ppl makein the same mistake as you and as it happens i have spoke to a audi tec mate who most prob had an answer for you shame realy

[Themadsinger]

Well, there you go. Self inflicted wiring problem - as I have said I really don;t think it is down to the wiring since the wiring has been there for some 9 months and whilst I cannot pin point exactly when the problem arose, it was certainly some time after my wiring was done.

I am not **** with this forum because no-one had an answer, it was annoying that everyone just came backasking questions when they clearly did not know what the problem was so why bother asking them - posts like "hahaha your system is *****" {paraphrased of course} is not constructive and wastes their time and mine.

No-one was able to tell me if there is a central control unit that should be looked at which suggests that either (i) no-one knows, which is fine - need to try some more knowledgeable sources or (ii)some-one knows but is choosing not to share, which again is their perogative but if that is the case, not the helpful input I was hoping for.

Even if someone came back and say that your wiring has probably ****ed the light conrol unit which is located -------, would have been a constructive and informative comment. Read back through the responses and none of them are actually helpful.

Also, coming in late with a comment like "I have a mate who would have the answer but now I am not going to ask him" could, at the late time it was thrown in, be interpreted simply as trying to make me feel bad but it does not 'cause I doubt whether it is true. If it is, my loss, but there you go.

Thanks anyway for taking the time to look at the post. I will let you know when I get to the bottom of it

Cheers

[Themadsinger]

So what you are saying is that you screwed up your cars electrics by treating a highly sophisticated electrical system as if it is a toaster, and now you're ****** with this forum because no-one here has clicked thier fingers and magically fixed it for you?



No - being asked the same thing again and again without anyone offering anything useful seems a waste of time on both sides when it clearly is not leading anywhere




Phone a sparky, pay the bill, and write it off as a learning experience.

PS: I'm sure you'll be just as welcome in any other forum as you are here.

Anyone who knows me will tell you that I am a very helpful person and go way way out of my way to help others both in person and on a number of forums relating to other areas. I do not have undue expectations of some miracle answer and it is not the fact that no-one had the answer but that they seemed, rather than admitting that, to go off on tracks which clearly weren't heading for any sort of answer. What caused the problem is helpful to know once the problem has been identified.

That is me done

Best regard

[Themadsinger]

No-one heard of a comfort control unit ??? Can get damp in and cause problems such as these, completely unrelated to the any wiring I might have done?

[toff]

No-one heard of a comfort control unit ??? Can get damp in and cause problems such as these, completely unrelated to the any wiring I might have done?


Hi,

I've been busy of late so haven't had chance to reply. My next suggestion was going to be this:

On a number of Audi models, the Central convenience unit, which controls the central locking, windows and possibly the lighting (I'm unsure) is located below the heater matrix (You have to remove the glovebox to get to it).

There were numerous cases (on A4 & A6's at least) where a one-way rubber drainage bung would gunge-up with leaves, the scuttle area would then slowly fill with water.
Eventually the water level would reach the level of the pollen filter and pour-into the heater matrix and down onto the central convenience unit, causing a a plethora of weird electrics problems.

So you could remove your glove box (just 6 bolts or less) to check for dampness or remove the pollen filter and check for dampness. Here's a link that describes the problem in more detail:

http://www.vwaudiforum.co.uk/forum/showthread.php?t=18305

I hope you fond that helpful?

Asking lots of questions when you don't know what the answer... that's called a process of elimination my friend. Whats more, we don't know you from Adam, we don't know how adept your electronics skills are; so there is good reason to ask basic questions; you might not have thought of them!

Anyhow.. as you point out yourself, it's much better that people try to contribute rather than keeping constructive comments / questions to themselves.

Also, bear in mind your description of the problem isn't easy to comprehend.

I'm not intending to be spiteful or rude but if you check for dampness and find nothing; you should pay for an hours diagnostics with an auto electrician to get to the bottom of the problem. Let us know what it turns out to be.

Al.

[Flakmunky]

@ themadsinger:

The central convenience unit (CCU) is £200+ to replace. Therefore it is much cheaper and easier (I thought the CCU was under the passenger carpet so it is a seat out job) to remove your wiring and see if the fault still exists.

Reading through your post again, you say that you tapped in to the live from the glovebox light and then used a switched earth (this is the same way the CCU switches the lights on and off) but later you ran a new 12v feed from the fusebox. Am I correct in thinking that you reused the same switch and that at one point you had both wired in to the same switch but you now just have the phone charger connected?

When the switch is off (earth broken to your new socket) the lights don't work but the cigarette socket (the one you fitted) does? What about the factory fit socket? Have you tried a circuit tester yet? Where did you take the negative from for the GPS and the phone charger? Have you physically inspected the wiring? If you had both units drawing power at the same time you may have overloaded something?

When something goes wrong, I always blame the last thing that was done - whether on cars, bikes, computers, heating systems or whatever, which is what fellow members no doubt also thought.

Despite your wiring being in place for the last 9 months (but developing a fault sometime between now and you don't know when) that doesn't mean something hasn't gone wrong. You said you used Scotchblocks; these are considered by many to be a 'bodge' and are not as secure as solder.

Personally, I would never have tapped in to the glovebox light.

[Themadsinger]

Thanks Toff and Flackmunky for the helpful comments.

At the moment there is no wiring fed from the glovebox light feed - removed this a while ago, although after the fault arose.

The point of mentioning about this funny thing with the wiring is that when the internal lights are not working, and that is nothing to do with the position of the switch which I installed, there is an earth or negative leakage back through the live feed for the internal lights. This disappears when the lights start to work. This indicates there is some short somewhere and could therefore give weight to Toff's suggestion of damp in the central convenience unit.

Whilst I am not going to day that the wiring I did has not overloaded something, if it had I would expect that the lights would not work altogether.

I have used my multi-meter to check that I have not managed to break some wire somewhere and that there is good continuity to the glove-box light. The supply to the extra 12V socket which I fed from the cigarette lighter feed behind the glove box works fine and switches on and off with the switch. The cigarette lighter feed also works fine.

I will check for water where Toff's link suggested, although I ahev had the glove box out a couple of times and have not noticed any damp.

Thanks again both of you for the input.

[Flakmunky]

Intermittent faults are a nightmare... I agree it could be damp, but it could equally be a loose wire somewhere.

Good luck. Please let us know how you get on...

[Themadsinger]

It is not really intermittent. The lights will never work if the engine is off. Therefore they do not come on when the car is unlocked etc, which is the real pain when it is dark.

With the engine running, if I toggle the switch above the centre console a couple of times from the middle position to on they will come on and normally stay on - if I switch on of the front spots on and turn the main switch off, the spot will normally stay on and if I switch it off it will normally switch back on. Same with the rear light, but in each case only when the main switch has been toggled first.

What does the comfort unit look like as I cannot recall seeing any likely contender when I have had the glove box out in the past.

[Flakmunky]

Like I said previously, I was under the impression the CCU was under the carpet / seat in the passenger front footwell.

Have you checked the switch in the centre console?