Hi All,
Can anyone help me. I recently bought a 2004 Sonata which has been giving me a lot of grief as the alarm goes off without reason. The first day I had the car it woke me at 12.30am but the next night it was kinder and went off at 10.30pm. But it doesn't seem to have a set pattern as it can go off in the morning. When I was at work the other day it went off 3 times in the space of 15mins in the afternoon. I have had it to the local dealership and they can't determine the cause and of course it has "behaved" there. The only thing they could see was that the door had been repaired at some time but this was after they had replaced a boot seal as they thought water leaking into the boot was the cause. My only option is to disconnect the battery every night which is a pain as I haven't got the knack of resetting the stereo. I have talked to the dealership of totally disarming the alarm which I am disappointed that I have to do but it is winter here in Australia & I don't enjoy mucking around with the battery in the cold. Thank You

 

My guess is the switch on the door is misaligned or damaged from the repair. The alarm system uses the switches to determine if a door is open or not. If the switch is bad and gives a false signal that the door is open, that could cause the alarm to go off.

 

I agree with Nova I had the same problem with the passenger side door switch on my 04. Keep a eye on the inner door marker light while you pound on the inner door when its closed to see if the light flickers. It can easily be fixed by shims under the door switch.

 

Hi! We have just bought an '06 Elantra in New Zealand.
The alarm has been going off at irregular intervals. Three times one night so I had to disconnect the battery. GRR!
We read a few forums and remembered an aftermarket alarm we had on a Mercedes years ago...
Under the bonnet (hood) is a small plunger switch which activates the alarm when the bonnet is opened. If this is out of adjustment it MAY hold the alram off then activate unexpectedly.
NOW there is a 10mm dia rubber doofer pressed into the bonnet frame and it is this which pushes down on the switch. For some unknown reason ours was missing. VOILA and EUREKA!
Fortunately I found something suitable in the junk I acquired from a friend years ago.
Last night was quiet so hopefully, problem solved!
Look for the simple things first!!!

 

Sonata 04 you wrote: "Keep a eye on the inner door marker light while you pound on the inner door when its closed to see if the light flickers. It can easily be fixed by shims under the door switch."
That's my situation. Alarm going off at random, passenger door marker light is on even when door is firmly shut. My question to you or anyone: Can you be more specific about what is involved in putting shims under the door switch?
Thanks!

 

I wouldn't automatically assume the door switch needs shims. It may just be bad. Try depressing the switch by hand with the door open and see if the light goes out. If it doesn't then you should be looking at the switch or wiring to the switch as the likely problem.

 

Thanks Rallyman. Depressing switch turns door light out, so that seems OK. Light tends to go on when I brake, other times it's random. Driver's side door light is fine. Does anyone agree drivers side door light may be connected to random alarms, or should I be looking elsewhere?