# Rear hatch 'open/close sensor' flakey? Alarm going off on its own spontaneously.



## Thomas Smailus (Jul 8, 1999)

How annoying. 2002 NB - about 18 months old now. Just 2 weeks ago it started. In the middle of the night, the alarm on the beetle goes off. I go disarm it. It goes off again at 4am - OK, to really disarm it you need to open a door and then close it after disarming the alarm or else it auto-enables again. 
Fine, I think its maybe the rain that night and if the hatch wasnt fully closed (but the alarm did activate with the flash/beep), water may have gotten into the latch and shorted the contacts on the switch.
Its dry for several days, so we try locking/arming the car again. Again, it spontaneously goes off several hours later.
Take it to the dealer - they say the read the messages out of the diagnostic and it reports the drivers side door was open to set off the alarm. I did tell them we are pretty certain its the rear hatch circuit thats the issue since my wife tells me the 'hatch open' light would not go off or would intermittantly come on while driving (and the hatch was DOWN). Since they had 'adjusted' the drivers door several months earlier to correct a bad assembly of the car at the plant, that sounded feasible and if the obd says its the door, I'll buy but I'm still skeptical.
We get it home and that evening, the alarm goes off again! CRAP!
What the hell did they do to design this thing? The sensor should definitely know if a door is not fully closed (just partially latched or open) and then not engage the alarm (and display the status in the idiot lights). If its thinking its closed and later thinking its open it should be either 1) Someone opened a door, or 2) the switch or wiring or head unit is defective.
Anyone else having similar problems?
Is the hatch wired in to other circuits such that the obd could show a door warning only (and not an independant hatch warning)?


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## reflexbug (Mar 10, 2003)

*Re: Rear hatch 'open/close sensor' flakey? Alarm going off ... (Thomas Smailus)*

sounds stupid, but the battery could be junk... mine did that, and it still started fine and all that, no symptoms... then one day it was just dead, complete failure... I replaced it and it hasn't done it since. Go figure... MK3's are famous for that problem too...


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## Thomas Smailus (Jul 8, 1999)

*Re: Rear hatch 'open/close sensor' flakey? Alarm going off ... (reflexbug)*

That is indeed odd. Thing is the car runs fine and the car starts up lickity split each morning (even now that its finally cooling off in south Louisiana).
I did have the dealer adjust a spacing issue between the mirror and the door on the driver side that was causing wind noise at low speeds because the of an excessive gap btween two parts of the mirror. The fix was for them to pull in the door from the hinge side, tightening it down (I believe) - and that may have pulled some things out of alignment as I'm sure they didn't loosen and retighten every bolt in the door. The power window clips popped several months later - but thats a known problem. This time, they adjusted the latch and sensor in that drivers door.
I'll have to drive it myself this weekend to get firsthand knowledge about whats going on with the lights so I can tell the dealer next week what I'm seeing. The wife is not too up to speed on what to watch for and doens't always remember whats what.
The car is only 1.5 years old, so a dead battery would be very unusual - but I'll believe anything since the Pueblo plant let the Beetle out the door past QC with a mis-aligned door.
But if it did it for your New Beetle, then I'll be sure to mention it to the dealer service guy. My 94 Golf has never had a problem with the alarm due to a dying battery. I always know the batter has reached its end of life (3-4 yrs) when my dash clock starts loosing time overnight.


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## VdubMAN53 (Jan 3, 2003)

*Re: Rear hatch 'open/close sensor' flakey? Alarm going off ... (Thomas Smailus)*

whan u drive will the come lights come on???my car doen the whole alarm thing i fint that i have to jiggle the dore handle on the inside


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## searocko (May 18, 2001)

*Re: Rear hatch 'open/close sensor' flakey? Alarm going off ... (Thomas Smailus)*

Check your spare tire well for dampness. My 3rd brakelight seal was leaking, shorting out the rear hatch solenoid. Happened to me and my hatch-open light would stay on.


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## DennisC (Jun 29, 2001)

*Re: Rear hatch 'open/close sensor' flakey? Alarm going off ... (Thomas Smailus)*

Thomas,
I'm having the same exact problem. Only happens when it rains alot, latch light comes on very dim. I lock the doors and a little bit later the alarm goes off. Will take searacko's recommend and check the spare tire well for water. 
Searacko,
What do you mean by the third brakelight? The brake light mounted on the hatch??


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## searocko (May 18, 2001)

Yup, that's the one! Try pouring water over it while opening the hatch slightly. You can see the water dripping through the latch if it's leaking bad.


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## Thomas Smailus (Jul 8, 1999)

*Re: (searocko)*

I was way ahead of you guys on that - I already checked, but now I'll check again. That was my first thought, because it started after it had rained a lot and was very windy. I pulled the interior cover off (2 screws and a yank) to expose the insides, put some clean newspaper down on the bottom of the trunk) shut the hatch and then got the hose and applied some forcefull water in quantity to all the areas around the window in the back, the 3rd brake light and the rubber seal between hatch and body. I opened it after several minuts 'hoping' to find some water comming in around the 3rd break light. No such luck - couldn 't find any real water comming in. 

However, the first time it happened there was water on the latch mechanism - and THAT part is INSIDE the rubber seal - so I'm sure water got in 'somehow'. I cannot be sure that the wife had the hatch closed solid when that store happened, so it could have been initial water intrusion from the hatch not being fully seated.
However, it was dry for several days and has not rained since then, even the dealer had it in the shop and the wife had it out at work (some 10+ days after the initial event) and the alarm went off again (5th time at that point) - so I'm thinking by then, any water was dried out and it could not be water causing the problem directly. I don't know if initial water intrusion into the sollinoid could have gummed it up, but I'd doubt it. I'll go back and check again. The 'switch' that detects the latch being closed is in the latch itself. You can have the hatch all the way open and use your finger to engage the latch in the hatch-lock and the light goes off (use the hatch release button to release again before you shut the hatch







) Behind the hatch cover on the inside is just some wires as far as I can tell - nothing that was wet.
I'll check it again this weekend - but we have another dealer apointment on Tuesday to look at it all again (including a problem with the friggen radio where the level of the volume-to-mute transition keeps moving around to where you have a normal listening level and one detent turn further down is MUTE, so you get no quieter settings - and it varies with station and time - not sure what the patterns is - may just have them put in a new radio).


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## DennisC (Jun 29, 2001)

*Re: (Thomas Smailus)*

Thomas,
I went out (just a bit ago) and did a quick check for water in the spare tire well and general dampness. Everything was as dry as a bone. But there is definitely water under the lens of the third brake light. I can see the condensation. I wonder if that's all that it takes? 
Chances are that the latch circut and brake circut are the same and a water/short in the brake light is causing the alarm/latch anomaly? That's my theory and I'm sticking to it (for now).







Will remove the brake lens to dry it out at least. Any idea on how to get that lens off?? 


_Modified by DennisC at 2:54 PM 12-12-2003_


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## Thomas Smailus (Jul 8, 1999)

*Re: (DennisC)*

Now there's a thought. If a short inside the light causes enough of an electrical glitch, the alarm can misunderstand what the switch is saying.
I'll have to check that out. No light left for today, something for tomorrow.
Also, it'l get the wife to empty all the stuff out of her trunk.


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## DennisC (Jun 29, 2001)

*Re: (Thomas Smailus)*


_Quote, originally posted by *Thomas Smailus* »_Also, it'l get the wife to empty all the stuff out of her trunk.

DOH! If that were my wife, it could take all weekend to clean out.


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## Thomas Smailus (Jul 8, 1999)

*Re: (DennisC)*

Well, update. Its back from the shop - they called the 'vw tech line' for help in diagnosis and the tech line recommended replacing the ignition switch. Fine, once again no work done on the rear hatch circuit.
So we drive it home the 10 miles, park it just get into the house and the alarm goes off again. I go out open and firmly shut all the doors, hatch and hood. 30 min. later the alarm goes off again. Clearly VW has no clue what the problem is and refuses to listen to what I've been telling them since visit #1 - that the rear hatch red light in the dash is comming on occasionally when the hatch is clearly closed and its possible that THIS is the source of the alarm issues.
So I'll bring it by AGAIN some time and start fiddling with it with the tech.

If it was not still under warranty, I'd be in there myself with the DVM and some aligtaror clips trying things out but I know the way those jerks at VWoA are if you touch the electrical at all - suddenly anything wrong becomes an issue YOU caused. Got bitten once - now THEY will fix it. Next time it goes in I'm getting a rental car and start tallying up some more cost on behalf of VW - maybe that will motivate them a bit more.



_Modified by Thomas Smailus at 2:43 PM 12-18-2003_


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## DennisC (Jun 29, 2001)

*Re: (Thomas Smailus)*

Well crud.....sounds like I had a bit more success.
I removed the hatch panel (two screws and pop it out), and could see a good deal of condensation on the underside of the hatch, between (below) the third brake light and the cut out for the hatch handle/lock assembly. The hatch handle/lock assembly was not leaking, but the third brake module was loaded with water. 
There was a small sponge (3"x3") attached to the hatch panel that I removed, that was soaked with water. It apparently acts as a vibration damper and rests against the electric hatch opener. I got a hair dryer out and spent a good deal of time drying everywhere I could see water.......with the exception of the brake light module.
The latch warning light circuit was the culprit I'm sure as I unplugped a couple different circuits to test if the warning light would go out. The small plug that attached to the truck latch itself was wet and had a small amount of corrosion on it. Removing it, causes the warning light to go off. Prior to drying, it stayed on dimly and slowly went out as a result of drying. I dried the brake light module as best I could and put clingy plastic wrap over it to keep it dry, for the very short term fix, to keep the alarm from going off. 
So, water is getting in via the third brake light. I'm 90% sure it is water in the hatch open warning circuit and is most likely right at the connector with the latch........I will check to see if there is any water in the hatch switch at the drivers door.
Ultimate likely fix: seal or replace the third brake light module.




_Modified by DennisC at 3:42 PM 12-18-2003_


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