Since I changed out my OEM Becker head unit, my door LEDs have been double-flashing. I assumed my problem was with the head unit ground sensor, or the glove box switch, since I disturbed both during the installation. I've taped off the head unit ground sensor, and that didn't help. I've poked and prodded my glove box switch (the light works fine, and all functions associated with the glove box switch seem to be fine as well).

So, I decided to buy one of those T-OBD cables to use with Scantool, to read the Alarm codes. I figured its probably a good investment if I'm going to keep my 993 for a while anyway. To my surprise, the alarm module scan shows NO alarm codes are set. I reset and refreshed the display several times, and got the same result each time. I can trigger the horn-alarm by opening a door when the FOB has locked the car, so I know the alarm unit is functioning, at least at some level.

I wasn't expecting this development. Has anyone got any suggestions as to what to do next? Is there something else I should check with this tool before moving on to the manual method of checking inputs at the alarm module? Or do these results point me to something else entirely?

A nudge in the right direction would be greatly appreciated here... I'm at a loss. All of the alarm/double-flash posts I've found here, using the search, were about an alarm condition being set when locking the car, easy to find and fix. Now I'm not so sure that's my problem. Or I've missed something. I'm tracing the alarm schematics in an attempt to figure out what.

Thanks for any suggestions!
Rod

 

what do you mean by 'I've taped off the head unit ground sensor'
There is a green cable coming from the fuse box on top right behind radio , this should be hooked
to the radio chassis. If it is not, your leds will blink
The error message will not show on OBD.

 

The green wire must be isolated from electrical ground. In the factory configuration the green wire is connected to a spring tab on the receiver mounting bracket and isolated from the receiver chassis by a piece of tape. When the receiver is removed from the bracket the contact slides off of the tape and grounds to the receiver. If the alarm is set that ground through the receiver chassis sets off the alarm.

geolab is correct about the code on the OBD. The only readers that I know will see the alarm codes are the PIWIS, Bosch Hammer, or Durametric.

There is a fuse on the alarm control unit. I can't remember what happens when that is blown. I know there is a thread here on rennlist that discusses that. The alarm will double blink if fuse 11 is blown. If it's not a fuse, not the radio or the glove box, then you need to start down the list of other alarm inputs. The list is here on rennlist in several other alarm threads.

EDIT: If the glove compartment light works fuse 11 is good. Here's a thread that discusses in detail.

 

I realize that alarm status doesn't show in standard OBD readings, which are primarily engine and emissions status data. But T-OBD shows more than just OBD standard readings - it shows the status of the airbags, the climate control unit, the alarm unit and the tiptronic module as well as the Motronic DME.

Yup, Fuse 11 is fine, I checked it after reinstalling the new head unit. And the fact that all lights enabled by Fuse 11 function proves continuity. If I pull Fuse 11, the light don't function.

I haven't checked the alarm module fuse (the one embedded in the module itself next to the connectors), but my assumption was that if its blown, the alarm can't work at all - ie. no alarm-horn when opening a door when the car is locked from inside. Maybe that's not true?

I guess I'll dig out my multi-meter and start working my way through the alarm inputs on the module connector. What a freakin' PITA.

Thanks for your help, all the same.
Rod
PS: hoggel, that link is back to my head-replacement thread - R

 

Doh! Very helpful huh? Where's the dumbass emoticon?

 

Don't worry about it, hoggel - you were trying to help, and I get that.

 

^^^ I had a similar problem and it turned out the wires from the glovebox light had been reversed when the harness was re-installed ....

 

I don't see how reversed wires on the light would cause a problem. But if the wires to the light were swapped with the wires to the switch ... ? I think in that case the light would work but the alarm input would be grounded all the time (through the bulb). Could be the problem with your car. Check to see if the 12V wire (red?) is on the bulb, not the switch.

 

This is somewhat related, but not directly......

I connected the green wire to the ground connection on the back of my CDR-220. I originally had a CR-210.





As predicted, it set off the double LED flash. Disconnected and all was back to normal.

 

Yes, that's exactly right. Switched wires ... problem solved.

 

Disconnect the neg. battery terminal and put a digital multi-meter set on milliamps in series between the battery and the neg. terminal. Close the hood with the DMM outside and let the car go to "sleep". (Don't arm the system). If you read over 35-40 milliamps, you've got something that's not shutting off which would cause your alarm system to double-flash. Could be something so simple as the trunk light.

 

I wanted to go through the schematic for myself, and produced much the same sketch you did, hoggel, on the left side of your page. Assuming the Br/Gy and Br/W wires actually join AT THE CONNECTOR to the "bottom" of the light, then reversing the wires to either the light or the switch should make no difference to the alarm module: in both cases, until the switch is closed (box lid open), the alarm module doesn't see GND.



So the only way you could screw this up would be to reverse the connectors so that the alarm is connected to the bottom of the switch. In my car, the loom that carries the single cable providing both sets of connectors makes it almost impossible to do this: the connectors for the light won't reach the switch.

But WTH - knowing me, I found a way to swap the connectors. So - I'll take the box back out to confirm wire colours and connectors and see if that fixes my problem... because I touched so few things while doing the head install, it only seems reasonable to believe that the problem comes from either the head unit or the glove box. Since taping off the green ground wire to the head is pretty hard to mess up, that leaves just the box... Thanks everyone.

[ Edit -replaced original jpg with a corrected version, showing Br/Gy instead of Br/Grn alarm wire. 24-Aug13 - R ]

 

Well, I'm humbled by what I found...

I had INDEED reversed the connectors on my glovebox when re-installing, so the connectors that were supposed to go to the light went to the switch, and vice versa. As I was taking the inner liner out this afternoon, I remembered having a devil of a time getting the liner re-installed once done with the head unit replacement, because the wiring loom always seemed to be in the way... Duh! NOW I know why it was so hard - somehow I managed to swap the connector locations, and the cable was NONE too happy about it.

Bottom Line - I accidentally swapped the two sets of connectors, causing the door LED double flash. When I corrected the wiring per the drawing above, the lights all worked as before, but now THE DOOR LEDs SINGLE FLASHED as normal.

While I was fiddling with the glove box switch, I experimented a bit, and here's what I found:

- get in car, box lid closed, lock with key FOB, locks OK, door LED single flash
- open box lid - door LED single flash changes to double flash, no alarm horn
- close box lid - door LED returns to single flash, no alarm horn

- get in car, open box lid, lock with key FOB, locks OK, door LED double-flash, no alarm
- close box lid, door LED returns to single flash, no alarm

This surprised me - it means that the glove box being opened when the alarm is set doesn't trigger the alarm horn, and appears to be treated as a simple alarm fault. If the car top is up, then it doesn't matter since the box can't be opened when the car is locked anyway (and breaking in triggers the alarm). But if the top is down, locking the car doesn't protect the contents of the glove box via the switch and alarm module... so a tall, long-armed person could still reach in when the car was locked, rummage through the glove box, and walk away with your iPOD or phone without triggering the alarm horn. Moral of the story: don't assume locking the car will protect the contents of your glove box!

Anyway, I took some pictures of the glovebox and its wiring before putting it all back together, as well as the plastic slider rails and the light and switch. I show the switch in both states: lid open (plunger out); and lid closed (plunger in). Note that both the light and the switch are totally reversible: either tab can connect to either wire - all the switch does is complete the circuit between the two wires that connect to it.

Glove Box Switch shown Lid Closed, Plunger In, Switch Open


Glove Box Switch shown Lid Open, Plunger Out, Switch Closed


Glove Box Light and connectors


Glove Box Light & Switch Wiring - Light wiring top left, Switch wiring bottom right...
Note: wiring to the light: Red to one tab; joined Br/W & Br/Gy wires to the other tab (see dwg posted above)


Another view of the Glove Box wiring with its two sets of connectors


Globve Box lid with plastic slider rails that are inserted into slots in the dash - the driver side slider
goes into a slot just below the head unit and when the lid is closed sits just immediately beneath the head
so if you have wires down there, something is eventually going to go wrong.


Glove Box without Lid installed - slider rail slots are on either side of the liner - interestingly, only
the right slot has some kind of inner "grabber" to prevent the rail from coming out, while
the left rail just inserts into its slot and seems more like a backup catch if the right side slips out. Weird.

 

Congrats! I chased this and chased this after my car's conversion .. took the car to the dealer and had them read the code and the code number corresponded to: .. 'Glove Box Door' .. tech said it meant that the system thought the glove box was open. Wires were swapped back ... no more problems.

 

Thanks, JPP, for bringing up the swap as a possible cause... between you and hoggel, you set me on the right path. Thanks guys, GREATLY appreciated!!

Rod