Interior light trigger wire

[UrS4Eben]

Hi guys,

I was wondering if someone could help with the best connection place/wire colour at the relays under the steering wheel for a '92 S4 Avant?

I need to connect there for an alarm system that I'm installing but I cant find any diagrams for it even in etka

Any help appreciated

Thanks

Eben

[quattronutter]

i usually connect just after the interior light fuse, in the fuse box

[UrS4Eben]

I could do that but I dont keep my interior lights switched on....
which is why I'm looking for the switch wire rather.

[UrS4Eben]

Hi guys,

Just thought I'd update you all. It might help if any of you need to do the same:
The battery drain problem that me and some others have been having I also solved.

The door switch on the drivers door is most propably to blame.
In my case the switch never fully engaged when the door was open.
This caused the relay that keeps the lights in the windows buttons etc. on, to click all the time and keeps that circuit energized until the battery runs out.
Simple fix remove the switch, open it up and dismantle carefully as not to loose the spring inside. Rub the metal contact piece with fine sanding paper and stretch the spring VERY slightly. Reassemble and voila, your relays will switch off next time you close the door.

Now for the alarm fitting bits....
all the door trigger wires that I could find goes to the back to the central locking pump. If you are going to try and use the dome light as a trigger for the doors you might run into problems because of the light delay function ( your alarm will think it couldn't lock the door) So it is advisable to get the trigger wire where it goes into the central locking pump instead.

Next step... I need to look for a trigger from the luggage door at the back

I dont reckon it comes to the fuse area either

[sheppardnias]

Hi.... Slightly confused with what you say and am starting to doubt what knowledge I thought I had gained in the last week on my URS6.

I had a problem with the luggage lamp not working and traced it to the microswitch in the right lock mechanism which switches 0V to the lamp unit. The lamp is fed a constant fused 12V supply (red / blue wire) and the lamp unit has 2 positions. A) to a hard wired earth (brown wire) B) to a swicthed earth in the right boot lock. (brown and white)

The wire from the boot lock seems to go to the lamp unit and then off to the original alarm unit. Thus if you open the boot the alarm sees earth irrespective of your lamp being switched on or off.

On my car some bright chimp had wired a 12v feed direct from the battery into the switched earth on the luggage lamp. This fortunately never saw a real earth connection because of the broken microswicth, if it had I doubt the car would still be here.

Feeding 12V into the alarm caused my battery to go flat because the alarm kept getting fed 12V where it expected to see 0V. The alarm would try to set wait a few seconds and then reset itself continuosly. With a DVM you could clearly see the current spikes from this. Fortunately the alarm seems to have survived this assault but until I replace the rear fog lamp switch (the led has been cut out for the alarm) I won't know for sure that it is setting correctly.

I would be surprised if any alarm system should be switching on a 12V signal. Every car I have worked on has used 0V switching, a practice used in many industries for this type of signal. If you can pass signals around a car at 0V do so, when wires get nickes, chaffed, fall off or just plain butchered there is much less likelyhood of shorts happening and the resultant damage that can occur. You mentioned the light delay upsetting the alarm as well. In my experience when you lock the car the interior lights are switched of at the same time, ie the off delay is cut short. Is that not standard? The comfort unit knows the car is locked and removes its switched earth to the lamps allowing the alarm to set. No point leaving the interior lights on, you are outside the car.......

[UrS4Eben]

Hey there,

YOu are completely correct about how the luggage room light works but I didn't have an OE alarm so I dont reckon I have an existing wire going back to the front so I'll have to get one from the microswitch.

About the front doors: The alarm I'm installing has the possibility of either a + trigger(dome light going on when door is opened) or a negative trigger(door switch earthing). Because the negative trigger wires goes to the back I used the positive feed of the delayed interior light circuit as the trigger.

The light goes off when you lock the car but only a millisecond after the door has been locked, which makes the alarm think that the door didn't close....

[sheppardnias]

Ok... That makes sense I guess.

Is there no delay on the alarm while it checks the circuits and sensors? It seems crazy for a modern alarm to not allow any form of delay on interior lighting.

You could pick up the eart wire on the luggage compartment from the light unit, it will be easier than feeding the wire out though the conduit on the rear door but it will still be a real pain to get to an alarm unit I guess.

Not sure in my head how picking up a voltage feed to the lamps will be any better than an earth contact though. If the earth is switched by the comfort unit then the current draw will still be present until the unit decides to switch off the lamp.

Picking up the inputs to the comfort unit would be the solition in an ideal world but that sounds like a real pain to me. I don't envy you that at all..... I've been cursing my cars alarm system (seems to have 2 of them depending on key or fob locking) but suddenly they seem like the easy option..

I'll keep an eye on this and see what your solution is, just in case I have to replace / reinstall a new alarm system in the end...

[UrS4Eben]

LOL its not that bad really... just a pain to try work everything out with the German diagrams and I live right on the A205 (south circular) not an easy place to work with open doors

The alarm actually has a "comfort" dome light delay function as well for those cars that don't have it.

I'll report back later with all my sources/taps to hopefully make it easier for anyone who does this in the future.