2004 LS Factory Alarm and Rain

I have the 2004 Aveo LS @ 64000 miles, and it does the strangest thing. Since I bought it 2 years ago, the alarm never has armed when locking the car. However, if I drive it in the rain, the alarm not only arms but will also go off about 20mins-1 hour after locking it.

It does have the generic electrical issue(splicer 101 burned out, I simply wired the left head/tail lights to the passenger side, and No cluster lights) Along with my driver door lock fell into my door after the top bolt broke off which I have yet to repair due to weather.

So far I've check all the plungers for the alarm but cannot find, if there is one, a main unit to adjust sensitivity of the alarm. Ive very close to simply cutting the alarm wire in the door but another solution would be preferred if possible.

My father in law and I think it might be a grounding issue, or maybe a short but I have no idea where to begin looking for such thing.

Sounds like a plunger is completing it's circuit only when it's wet. When the car dries out enough, the circuit opens and the alarm is triggered.

Given that it happens when you drive in the rain, I would guess it is the hood sensor. Trying spraying each sensor, one at a time, from a garden hose and see if it will let you set the alarm. If it sets, that one's your problem.

Edit: Once you've isolated the bad plunger(s), you can start trying to diagnose if it's a wiring issue or the mechanics of the sensor itself. Depending on the cost, I would consider replacing the sensor first then move onto tracing the wiring if that doesn't fix it.

Edit #2: The 2009 Service manual references a tamper switch attached to the door lock cylinders. Your 2004 might have something similar that could be the cause of the problem. Text below

Quote:

Theft Deterrent Switch

The front doors and rear compartment are equipped with tamper switches. The tamper switch attaches to the lock cylinder. The tamper switch activates by movement of the lock cylinder. The tamper switch activates under the following conditions:

Rotation of the lock cylinder caused by forced entry
The in-and-out movement caused by forced entry

Additionally, use the tamper switch in order to disarm the system. The switch grounds the disarm input to the remote control door lock receiver (RCDLR) when the lock cylinder turns in order to unlock the door. The switch is serviceable. Remove the switch from the door latch in order to service the switch.
Mechanical failure and/or corrosion on the switch may cause the system to self-activate intermittently. Inspect the lock cylinder for looseness if this happens. Any movement of the lock cylinder with this switch can cause the switch to activate the alarm. One possible cause for this problem may be a lock cylinder retainer that is not firmly installed to the lock cylinder. Reinstall the lock cylinder retainer or replace the lock cylinder retainer with a new retainer in order to correct this problem.

If the turn signal lamps flash once when the LOCK/UNLOCK button on the transmitter is pressed, that means the content theft security system alarm was triggered.

Thank you, I will check these out when the weather permits.