~ Anno Domini

Hi everybody. I hope you are doing well.

I have an 1989 and a couple weeks ago
the alarm went off in the middle of the
night for no reason. I ran out, used the
key to disarm the alarm and started to
scratch my head.

From there I started the car and drove it
around the block thinking that might re-
set the computer/alarm. While driving, I
noticed the lights behind me (seatbelts
lights on both sides) were flickering as I
drove. And I realized I could make them
flicker too if I swerved the car from side
to side or went around a sharp corner.

I parked the car, locked it, and those
same lights flashed on and off for the
rest of the night on average every 15
seconds or so. Off for about 10 to 20
seconds, and flash for 1 second. This
continued until I returned the next day.
PS, the interior lights only flashed like
that that night.

The next day is when the alarm started
going off when I closed the door. When
I lock the doors with the power lock and
then shut the door the alarm goes off
immediately. I disconnected the battery
over night and oiled the door ajar light
switches on the back of each door where
the hatch release switches are and that
seemed to stop the alarm from going
off when shutting the door, but now it
goes off intermittently. I disconnect the
baterry at night.

PS, the one lead I have is about 6 months
ago while I was driving the "door ajar" light
came on. I narrowed it down to being the
drivers side door ajar light switch, but it
stopped so I didn't think twice about it.
But investigating this problem I noticed
when I open the drivers door when the
car is running the door ajar light does
not come on the dash panel as it should.
The passenger side triggers the "door jar"
light when it's opened, but not the drivers
side.

Could the Door Ajar switches trigger the
alarm? Could this be related to the door
ajar light? Thanks so much.

The Green Hornet

That would be my guess

Hooked on Vettes

The two lights mounted on the sides of the targa
pillar are called the cargo lights. Since the
foot well and door lamps did not come on,
that would indicate the rear Hatch Ajar switch was causing
the cargo lamps to come on.

Once the alarm is set, the system monitors the two
door jam switches which are mounted on the backside
of each A pillar (by the front door hinges) and the
rear Hatch Ajar switch.

The Door Ajar switch only lights the Drivers Information
Center Door Ajar lamp. It serves no other purpose. So it
does sound like you have two separate problems.
As you mentioned, the Door Ajar indicator should come on
when either door is opened and the ignition is On.

The rear Hatch Ajar switch is located next to where the rear
glass latches. You can see the switch plunger when the
hatch is open. Either the switch is bad, or the latch
mechanism or switch needs adjusting.

Set the alarm and with the palm of your hand, press down
and release the rear glass a couple of times and see if you
can get the alarm to go off. You could also disconnect either
of the two wires going to the Hatch Ajar switch and see if that
stops the alarm from randomly going off.

~ Anno Domini

Wow, I am so grateful. Thank you. You
have given me some hope that maybe
this problem can be solved. You're right.
The foot well and door lamps did not come
on that night the alarm went off. It was
*only* the cargo lights that were flickering.
I went outside after reading your post and
sat in the car, closed the doors, and opened
the hatch by itself. Sure enough only the
cargo lights came on. So this is a good lead.

This is VERY helpful to know!

So the Door Ajar switch cannot trigger the
alarm. I wanted to know this. This is *SO*
important to know in my situation. Thanks.

YES, I think I am going to have to get new
Door Ajar switch OR try to fix/oil/whatever
the old one on the drivers side door as it's
the one that isn't lighting the Drivers Info
Center Door Ajar lamp. The passenger side
door ajar switch/light works fine.

Thank you. Extremely helpful.

OK. I am going to follow these instructions.
It may take me a little while to narrow things
down, but I'm so grateful for the tip. It gives
me hope that maybe we have something here.
I will report back. Again, so appreciate it!

~ Anno Domini

OK, I set the alarm and with the palm of
both hands, I went to the back of the car
and pressed down on the rear glass a few
times to see if that could get the alarm to
go off. The alarm did not go off. I tried a
repeatedly.

From there I inspected and oiled the rear
Hatch Ajar switch located next to where
the rear glass latches. I could not tell if it
was faulty. There was no corrosion and it
looked to be in the right place. I thought
about adding a couple washers underneath
the switch to lift it up a bit, but decided to
disconnect the main wire to it to see if that
stops the alarm from randomly going off. I
only saw one main wire. That is the one I
disconnected.

So we shall wait and see now. I feel like I
baited a hook and I'm waiting patiently for
the big one. I am still going to disconnect
the battery at night though. It's just not
fair to the neighbours to have that horn
*honking honking honking* at 3am in the
morning. I don't like it either. It is not fun.

Will update when any news comes. Thanks.

~ Anno Domini

Note: I have two threads and I'm trying
to fit them into this one.

Update: Right now I have decided not
to arm the alarm when the car is sitting
until I can find some answers. I put the
window down, locked the car, reached
through the open window to unlock the
door and the alarm did not go off. That
is such a relief. Until I can figure out why
the alarm's going off randomly I will have
to lock the car this way.

I have also disconnect the main wire
going to the Hatch Ajar switch which
is located next to where the rear glass
latches to see if Hatch Ajar switch is
faulty and causes the alarm to go off,
but I have not been able to determine
this yet. I have armed the alarm and
shut the doors (with Hatch Ajar switch
disconnected) and the alarm has not
sounded yet, but this will need more
testing. The car's sitting outside with
the alarm armed, Hatch Ajar switch
disconnected, and so I am waiting for
the horn to start honking. If the horn
starts honking when I shut the doors
or if the car's parked, then it's not the
Hatch Ajar switch. I hope this test is
right.

In the meantime, after unplugging the
rear Hatch Ajar switch and not knowing
if that is the cuprit yet waiting to see if
the alarm goes off, here is my question:

What can triggers those cargo lights to
flash in the first place? What makes the
cargo lights turn on in an 89 corvette
under normal operation? Is it only the
rear hatch? I'd like to know all reasons
those lights can flash. I mean, should I
investigate both cargo lights back to the
rear Hatch Ajar switch? The cargo lights
flickering could be a major clue or a lead
to what's going on here. What do you
think? Thanks a lot for your thoughts.

Hooked on Vettes

Here's the schematics that answers your questions.
If only the cargo lights come on, it's because of the
Hatch Ajar switch. You could have a wiring problem
but not likely.

Either Door Jam switch when the door is opened will
cause the Foot well lamps, Door lamps, Cargo lamps
and Spare Tire lamp to come on.

Turning the Head light switch all the way counter clockwise
will also turn all of the Courtesy lamps on.

First schematic shows when the Hatch is opened, the
contacts inside the Hatch Ajar switch close. and grounds
the two Cargo lamps which will cause them to light.
It also places a ground on Pin C of the Theft Deterrent
Controller causing the alarm to trigger if it is set.

Second schematic shows the RH and LH Door Jam switches.
LH Door Jam switch (driver side) has 3 wires. The wires are
grounded when the door is opened.

Tan wire will cause the chime to ding when the key is in the ignition and drivers door is open (ignition off).

Yellow wire places a ground on pin D or the Courtesy Lamp
Delay Timer. When this happens, the Courtesy Lamp Delay
Timer activates all of the Courtesy Lamps.

The Light Blue wire places a ground on pin J of the Theft Deterrent Controller which activates the alarm if set.

The passenger side Door Jam switch works the same way except it only has two wires. It does not have the wire to trigger the chime.

Since your problem is intermittent, it's going to take
some time to eliminate the problem.

~ Anno Domini

Thank you so much for this info!

Only the cargo lights flickered that night, so
if I'm lucky it sounds like it could be a faulty
Hatch ajar switch. Boy, that would be nice.
I'm a little cautious though because it would
be too easy if it was just that little switch. I
am afraid. :-)

Btw, I had to disconnect both rear window
defrost clips a few years ago because the
defrost lines on the back glass had some
breaks in them. When I was inspecting the
cargo lights yesterday I looked at them and
the one on the drivers side was melted a bit.
The black plastic around the metal looked
a little melted. Do the rear window defrost
clips have anything to do with the alarm
system or the cargo lights?

Lastly, this'll probably be a silly question,
but what part of the car should I go to
first to find the schematics wires. Do I look
in the door jam or maybe under the hood
or do the wires travel from the front of
the car to the back? I think this will help
get me started on the next part of my
investigation. Thank you. You've been
incredibly insightful!!

~ Anno Domini

Just an update:

I have been arming my car alarm
during the day with the Hatch Ajar
switch disconnected and so far the
alarm hasn't gone off. I have been
running this test the last 2-3 days.

The test:

If the horn starts honking while the
Hatch Ajar switch is "unplugged" then
it's not the Hatch Ajar switch causing
the alarm to randomly go off when I
lock the car with the power locks.

Note:

During the night, I lock the doors with
the manual locks (I don't use the power
locks or the key) so the alarm won't arm
itself. I am only monitoring this during
the day time.

PS, this test is based on "Hooked on
Vettes" excellent observation in post #3.

I'll keep you updated. Thank you.

~ Anno Domini

PROBLEM SOLVED!!!

I would like to thank everyone who
responded to this thread especially
"Hooked on Vettes," for helping me
figure out why the alarm would go
off in my 1989 vette when I armed
the car alarm and shut the door.

Post #1 has the story.

Anyway, the problem was a faulty
"Hatch Ajar switch." I figured this
out by following Hooked on Vettes
suggestion, which was to arm the
car alarm with the Hatch Ajar switch
disconnected. See post #9.

Well, after I disconnected the switch
the problem stopped. The alarm no
longer goes off at random. It's been
over a month now and no problems.

I am *SO* relieved! :-)

Thanks to "Hooked on Vettes" again!
You're the one that came up with the
solution. You deserve all the credit!!

Of course, as an "Independent Baptist
Christian" I give thanks to God above
all. I was praying for the solution. :-D

Oh, by the way, I haven't bought a
new Hatch Ajar switch and replaced
the old one yet. I have disconnected
the faulty switch for now, as I don't
see any rush to get the new switch.
I know there's a slight risk. Y'know,
if someone breaks the backglass the
alarm won't go off, but I can still arm
the car with the side doors so there
is still some warning against thieves.

PS, thnx to everyone who answered
this post too. It helped while trying
to solve the problem.

baas85

I just received the second door ajar switch the other day, and installed it.
The car still is not right, it will just blow the horn while I'm driving and sometimes random without the car on. For now I'm running it, without the security module plugged in. Which may be how I fix it, cause everything seems to work just fine without it. Who knows, it may be the bad part. When I can find a new or a good used module I may plugged it back in and check it. Anyways glad yours is fix.

~ Anno Domini

Hi.

Just letting you know "Hooked on Vettes"
said the Door Ajar switch only lights the
Drivers Information Center Door Ajar lamp
(ie, the "door ajar" warning you see on the
center panel). It serves no other purpose.
That means that switch does not cause the
alarm to go off at least in a 1989 corvette.

Here is the post about this:

Alarm goes off closing doors

Note: I'm not sure where you are in your
situation, but when I found out the Door
Ajar switch cannot trigger the alarm, this
REALLY helped me because I was able to
eliminate it as one of the causes.