nine9six

Please check your front trunk switch and report back your findings. Might want to search on trunk micro-switch.

nile13

Actually... follow these steps:

1. With ignition off, pop the trunk open.
2. Make sure trunk light is ON.
3. Push down the trunk latch. It's a bit hard but can be done with your fingers or a small block of wood.
4. Make sure trunk light goes OFF.

Report here whether it went OFF.

BTW, pop the hood release from inside the car after this procedure to be able to close the good again

enjoytheride

Interesting, here's what I've found: I set the interior lights to the 'Door' setting and they illuminated. I opened the trunked and noticed that the trunk light was not on. I removed the trim piece to get full view of the trunk latch and the microswitch. I unplugged the the microswitch connector and then the interior lights went out and the trunk light came on. I reconnected the microswitch and the lights swapped back again. I then manually latched the trunk latch which fully engaged the microswitch and the lights swapped back once more.

I disconnected the microswitch again and toned-out its connector. I found that the switch is open-circuit when depressed (trunk closed) and shorted when the trunk is open/unlatched.

Bottom line is that the interior and trunk lights activate in negation. And although now for some reason the interior lights are turning off after a second (with the doors and hood closed) the trunk light remains on which will eventually kill the battery.

Someone mentioned alarm diagnostic codes? No idea what those are, but the LEDs on the doors flash twice when the alarm is armed...

nile13

LEDs double-flashing are an indicator of a fault with alarm system. More specifically, probably an indicator of a fault with your front trunk microswitch based on what you've described.

Me no likee your trunk microswitch behavior. Let's see. Is it possible that your microswitch connectors are swapped?

enjoytheride

Not sure what you mean by 'swapped'. The connector is keyed to only plug in one way, though it shouldn't matter since the switch simply opens or closes and shouldn't have any polarity.

nile13

We'll discuss theory a bit later (I used to be an EE). If I'm to believe the schematics, the switch should be normally open. I can try and ohm it out tomorrow if I have a chance. Perhaps someone can do it before then.

nine9six

The lights turning off after a few seconds is normal operation (timed delay).

Based on what you wrote, (the trunk light remaining on) I bet you have a ground short in the trunk light assy, and/or possibly a faulty trunk latch micro-switch as indicated by the behavior you described.

I agree with the statement above...

Gently pry your trunk light from its recessed seating area, and try actuating the micro-switch and report back your results on the trunk light and cabin lights behavior.

If things operate correctly, then I believe you have isolated/identified a ground short in the trunk light socket area.
You can try to identify/isolate by adding maybe 4-5" of shrink wrap to the wires running to the light, which are possibly chaffed. I've seen where the metal connectors that hold the bulb, rock to the point of contacting the metal hood in the socket area, thus causing a short. Please check these failure modes and report back.
HTH,

hoggel

Something crazy here. The cabin lights and Luggage Light should operate together. Interesting that initially it seemed to be a problem with the cabin lights but they seem to work correctly with the trunk latch circuit? See the simplified schematic from the manual (Coupe, not RS) below.


Operating as it should.

Just posted this in another thread from the Diagnosis manual ... even though it is not mentioned the schematic shows the luggage compartment light operates with the interior lights.
"The interior lights are no longer controlled directly via the door contacts. The interior lights are switched on:
1. By unlocking the doors.
2. By locking the doors.
The lights continue to be lit for approx. 20 seconds
The interior lights are switched off(doors closed):
1. When the ignition is switched on.
2. When the doors are locked."


When you activate the alarm system the LED on the door should flash rapidly (2 Hz) for ~10 seconds while the alarm self tests.

If the system has no faults then the LED will begin a slower (.5 Hz) single flash.

If the alarm system has faults it won't flash for the 10 seconds during the self test and will double flash after the self test.

The self test will fault if:
the doors are not closed (or a door switch is bad)
doors are not locked (or a bad door lock switch)
hood is not closed (or bad switch)
luggage compartment is not closed (or bad switch)
alarm horn is not connected
glove compartment not closed (or bad switch)
radio not fitted correctly (or aftermarket head unit not properly isolated)
parcel shelf switch on cabriolet
fuse 11 blown or missing

enjoytheride

I finally had a little time to dive back in today. I removed the trunk light fixture while lit and the light went out immediately. I couldn't see where, but it must be grounding to the hood. I checked all fuses and Fuse 11 was blown, and will blow new fuses immediately if replaced. Clearly there's a short somewhere...

nine9six

as I suspected...

You can try to identify/isolate by adding maybe 4-5" of shrink wrap to the wires running to the light, which are possibly chaffed. I've seen where the metal connectors that hold the bulb, rock to the point of contacting the metal hood in the socket area, thus causing a short. Please check these failure modes and report back.

enjoytheride

The spade connectors that attach to the light look fine and are insulated well. The light bulb immediately turns off as soon as I unseat the plastic housing away from the hood. And even then, with the spade connectors disconnected and safely away from the hood, fuse 11 still blows instantly. The short must be somewhere else.

From your post-it note circuit schematic it looks like the 12V lead comes from the fuse, and the other goes to some other junction element? Does fuse 11 connect straight to a 12V bus on the other side?

hoggel

Sounds like the 12V wire is chaffed in the hood somewhere.

The power side of fuse 11 is connected to terminal 30 (permanent positive) within the Central Electric (where the fuses are in the front compartment).

Fuse 11 feeds four circuits in the coupe, not RS. Three of the circuits are the Luggage Compartment Light (pin K43), Glove Box Lamp (pin K43), and Engine Compartment Light (pin K41). The fourth circuit (pin K44) feeds the Ignition Lock Light and through the Ignition Lock Buzzer Contact to the Gong Relay, the Immobilizer Control Unit, and to the Speedometer (in tiptronic cars).

If you want the part of the schematic that shows the interior lights circuit send me an email.

Cchief24

I was looking for some information about an issue that I am having with my 98 993 Cab. the buzzer/gong came on a couple of weeks ago and stayed on for the entire trip. It has occurred again three times. I noticed the interior light on with the doors closed ( the interior light was fixed some time ago, worked fine until recently) I pulled the bulb and on Sunday I was able to locate the gong/buzzer and pulled that...today I took apart the door switches and managed to get the interior light working as it should for about two minutes...then it stayed on permanently so I pulled the bulb.
The luggage compartment light and the glove box light work fine.
Can anyone point me in the right direction to at least get the interior lights working....I don't care about the buzzer. its really pleasant without it.
Thanks

enjoytheride

Problem solved: the +12V wire was in fact chaffed in the hood. Thanks for helping me track this down!

nine9six

Well I'll be darned...