'97 chrylser lhs alarm system: false alarming

Last Edited By Krjb Donovan
Last Updated: Mar 11, 2014 07:45 PM GMT

Question

QUESTION: Hi, I have a 1997 chrylser lhs 200,000+miles. Has been great car been thru 2 kids learning to drive. My daughter is driving it now and the car alarm will just start going off for no apparent reason. It went off 4 times at school. She used the key fob to unlock and relocked the door and it stopped but then went off agin about a half hour later. This day was very windy. It was setting in the shed a while ago and just started going off. No wind there. I have tried a few things and can not make it go off ie. rocking the car, trying to open doors, tyring to open the trunk. Any thoughts on how to fix this. Thanks Bill

ANSWER: Hi Bill, The chances are that one of the door ajar or the trunk ajar switches is not being pushed in far enough so that it falsely reports that someone has tried to open the door/trunk. But because you say that you have tried all of these possibilities then about the only other approach would be to avoid 'setting' the alarm system when securing the vehicle. You do that by not using the outside door lock key cylinders, or the inside power door lock feature, or the key fob to secure any of the doors. Rather you secure the unlocked doors by simply pushing down on the mechanical lock button on the inside of each unlocked door. That should prevent false alarming so long as you remember not to use anything door locking function that involves electrical actuation which is what 'arms' the system. But it surely sounds like one of the 5 ahar detector switches is at the margin. Most likely it is the one for the most used door, the driver's. So you could try moving the door latch striker in the door frame abit inboard so the door is secured more tightly against the frame; also check the trunk latch for being too loosely set. Please 'rate' my answer (see below), thanks Roland

---------- FOLLOW-UP ----------

QUESTION: Thanks a lot.I read the manual and it says that the red activation light on the dash should flash for 15 seconds after activating the alarm. It does not do this it just stays on. It goes on to say that if it just stays on for the 15 seconds there is a problem with the trunk circuit. Is there some way to disconnect the alarm system? A fuse you can pull or something. Can you jumper the switches? Thanks Bill

Answer

Hi Bill,

Unfortunately you can't disconnect the system alone as it is built-in to the body computer. All you can do is try to not activate it. 

Because of the indication of a problem with the trunk part I would try to trace the wire from the trunk ajar switch to the body computer. The computer is just in front of the driver door opening and has 4 multi-wire plugs (gray/black/white/blue). You will find that the trunk ajar switch has a black/white wire that goes from pin 1 at the trunk release switch to pin 1 of the number 1 plug at the body computer (gray plug color). The circuit also requires that there be 12V supplied on the pink wire to the number 2 pin at the trunk release switch, so check that out as well as if the wire were open somewhere from the splice at the instrument panel back to the trunk then that would cause the light to stay on as you described because the body computer doesn't 'see' the 12v coming back from the switch. When the light is off on the dash the system is disarmed. I would very much appreciate your rating of both of my answers (see below), thanks. Roland

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