How to remove or deactivate the alarm?

If factory alarms could be bypassed, the criminals could do it, making them worthless. A better solution is to look at the age of the battery. I had this happen to my '93 Dodge Dynasty. That car sits most of the time, and after a few months, the voltage dropped low enough to cause false activation of the alarm. All cars today have a small drain on the battery to keep the memories alive in the multiple computers. Chrysler used to say, "a good, fully-charged battery would be strong enough to start the engine after sitting for three weeks". Today that is the industry standard unless specified otherwise by the manufacturer. A battery that's just two years old may not last that three weeks.

The solution for my Dynasty was to replace the seven-year-old battery, but later I unplugged the "IOD" connector that's used for storage. If your battery is fairly new, a better option might be to have your mechanic install a switch that disables the horn. There's multiple ways that can be done. If it comes to that, I can post the diagram with suggestions of which wire to cut and run to the switch. That won't prevent the alarm from activating, but flashing lights won't wake up your neighbors.

The idea of the noise and flashing lights is no criminal wants people to see what he is doing. The alarm scares him away even if no one responds to the alarm.

If a professional thief wants your car, no alarm is going to stop him. They can pull the cars onto flatbed trucks and haul them quietly to their chop shop without the alarm ever activating.

On most models, the alarm is not turned on if the doors are not locked with the key fob. Mine can be locked with the key or by the knob on top of the door, without turning the alarm on. There will be some type of light flashing on the dash or instrument cluster to indicate if the alarm is live when the door is closed. On my Dynasty, that light flashes for 16 seconds. It's a big yellow light. On my Ram truck, a small red light flashes about once every two seconds, but I don't know for how long.

Another issue to keep in mind is whether or not your model comes standard with a factory alarm has a bearing on your insurance rates. The alarms prevent the engine from being started. This pertains more to the young joy rider who is stealing a car on a dare and has no desire to sell parts from it. He is more likely to crash it and run away. Insurance companies see the alarm as one more obstacle to that theft. With aftermarket alarms, the insurance company has no way of knowing the system is installed properly, is working, or has been disabled after the discount on the premium has been granted. For that reason, they may not offer the anti-theft system discount for aftermarket products.

Your statistic of one quarter of vehicles having alarms would have been accurate in the early '90s. Today there's just a few models that don't have a factory alarm built in. A bigger deterrent to professional thieves is all of the computer modules are electronically locked to each other, so they have no value to those thieves, and they have no value to legitimate salvage yards. Those computers won't turn on in other cars. In most cases, when a computer fails on your car, you can no longer buy a good used one. You are stuck going to the dealer and paying a really high price for a new one, (as long as they're still available), and paying to have them program it to your car. Whether it's higher insurance premiums, or seriously higher repair costs, you and I are paying for car thefts, even though those expensive deterrents haven't stopped car thefts.

Not a weak battery. The issue is its age. Over time, the lead flakes off the plates reducing the amount of electrical power it can store. It can still start the engine just fine, but when sitting overnight, it can allow the system voltage to drop just enough to get the alarm system excited. An aged battery is just one thing to consider when the alarm is activating for no known reason.

The alarm on my truck activates at times on its own. I found the cause to be me bending over when the key fob was in my pocket. Sometimes the doors would lock or unlock too. To prevent that, I leave the key fobs in the house now when I'm working outside.

A less common thing to look at is switches out of adjustment. Your alarm is set off if the hood, trunk lid, or any door is opened before the alarm is turned off. Try lifting the hood and trunk lid without unlocking them. If tugging on one of them sets the alarm off, check the adjustment of that switch.

The only diagram I can find is for the base horn system, in the diagram below. The only thing shown running the horn relay is the horn switch on the steering wheel. The alarm system has to enter in there too, but since it's not shown, I added the pink and black arrows to show the next best places to cut a wire if you want to add a switch to silence the horn. I strongly recommend to not dig into the fuse box as it's possible to create all kinds of new problems. Instead, cut the pink wire that feeds the two horns or the black wire that is the ground for both of them.

The horn circuit is protected with a 15-amp fuse. A ten-amp switch will handle the current just fine when it's turned back on and the horn is used.

I found two different drawings to show the location of the horn, but there's some confusion here. In the middle image, it's called the "burglar horn". In the third image, it's just called the "horn". That implies they're two different horns, but they're shown as being in the same location. If these are indeed two separate horns, it would be a simple matter of unplugging the burglar horn. Don't do that if there's just the one horn for both functions. Doing so could leave you open to liability issues or the inability to warn someone.