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Alarm goes off randomly on RX450h

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Old 10-29-12, 05:40 PM
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jbx
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Default Alarm goes off randomly on RX450h

Looking for some advice on what to do next and maybe what to tell the dealer to look for. The factory alarm on my wife's 2012 RX450h AWD has started going off 2-3 times per night usually between midnight and 7am (it happened once on a saturday around 11am, but otherwise its always at night). It's not every night, but it is frequent...roughly 2-3 nights per week. I have to park it on the street, no garage or driveway in my area. Every time it happens, I look out the window or go outside and there is no one around, no cars just drove by, no cats, raccoons, etc. near the car. Happened once about 5 weeks ago, then it was fine for 3 weeks and started in again, but more frequently recently.

I bought it about 2 &1/2 months ago from a Lexus dealership in a different state...It was a dealer loaner previously. I have 2 key fobs....one for me and one for my wife (she is the primary driver). So far (as far as we know) the alarm has only randomly gone off like this while we are both at home (night time)...this made me guess that maybe it was a key fob problem, so I put a new battery in each key...that did not fix it.

A coworker said that maybe the dealership could adjust the sensitivity of the sensors (he was thinking maybe just wind or something was setting it off)....I took it in today and they said there was no way to do that on this vehicle and that they inspected the alarm and it seemed like everything was okay to them. I felt like I was kind of just blown off. When I reiterated to them again how frequently it happened and they agreed to keep it and look at it again tomorrow. I asked if they could just turn the alarm off (not ideal, but if it got me a full nights sleep I'd rather them do that then nothing) and they acted like that wasn't possible, but I never got a really clear answer from them.

I have pretty low confidence level that the dealership will be able to do much. Assuming that whatever the dealer does next does not fix this problem, any advice on what to try next? I was thinking that maybe one of the key fobs is just defective since it only happens when both key fobs are at home...so maybe I should just take the battery out of one and my wife and I can share a single key except in rare cases I could just pop a battery in the extra if needed. Coud a bad key fob even potentially be the problem?

Another thing I have read is that a low car battery could cause the alarm to malfunction. I can't imagine it needs a new battery with only 15,000 miles on the car, but I was thinking that for $100 or so that it might be worth just replacing it in hopes that was the problem.

Any other ideas, advice, or thoughts on what to try next?
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Old 10-29-12, 05:56 PM
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some sort of radio interference is my guess. I cannot park my cars locked in my garage because of the same problem so I leave them unlocked. I have yet to find out what is causing it as it happens to two brands of my cars
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Old 10-29-12, 07:28 PM
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Jason, welcome to C/L. You've got a nice car

Since you said you park it outside in the street, you might want to look under the panels and under the car (really well) to see if some critter might have crawled up in it at night for warmth (might be shorting something out). Other than that, I'd check with the dealer. Next time it happens record it on your cell phone and show that to the dealer. It's not a normal occurrence on that car.
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Old 10-30-12, 03:42 AM
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Interesting discussion. For my edification, other than opening the doors or hood while the car is locked what else would "normally" set off the alarm? Other than the door position switches in the door jambs and engine compartment, what else is there? (Glass breakage is an option) When someone tells you to adjust the sensitivity of the sensors, what sensors?

I've seen some discussions that the door position switches are not working. JBX have you noticed your interior lights on when the doors appear to be closed? If you have a failing door switch, you'd see that happen. Not sure you would see anything unusual if the hood switch was failing. You'd get a message the hood is open when starting the car. With bad door switches you'd probably get random dinging when the car is unlocked or it won't lock as it sees a door open.
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Old 10-30-12, 03:57 AM
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RXSF, does your problem occur day or night? Does it occur immediately adjacent to, but not in the garage? What's powered up in the garage? Refrigerator/freezer/furnace? Probably not a furnace in SanFran.
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Old 10-30-12, 06:59 AM
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DunWkg: I have not seen any interior lights on at all when I expected the doors to be locked, but that is a good thought...I'll keep an eye on that for sure. I haven't received any hood open errors either.
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Old 10-30-12, 07:00 AM
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Have had a similar experience with our 2010 RX450h, although so far only 3 instances each at about 11pm. I'm calling the dealer in Brisbane, Australia tomorrow
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Old 10-30-12, 07:17 AM
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Do you have the 'glass break' option on your RX? If you do, there is a sensitivity adjustment for that. Just a thought.
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Old 10-30-12, 07:25 AM
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I have only had my 2011 for 3 weeks. It happened to me one time. I believe it is related to the door sensor on my driver's side. Basically the door sensor doesn't retract all the way when you open the door, you will notice you have the door light, but the interior or dash light won't come on showing you open the door. You can actually test the switch by pulling it in and out manually
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Old 10-30-12, 08:48 AM
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Originally Posted by MEP7557 View Post
Do you have the 'glass break' option on your RX? If you do, there is a sensitivity adjustment for that. Just a thought.
No clue...since I bought it used...is there an easy way to tell -- other than breaking the glass to see ?
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Old 10-30-12, 09:53 AM
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Originally Posted by cossie1600 View Post
I have only had my 2011 for 3 weeks. It happened to me one time. I believe it is related to the door sensor on my driver's side. Basically the door sensor doesn't retract all the way when you open the door, you will notice you have the door light, but the interior or dash light won't come on showing you open the door. You can actually test the switch by pulling it in and out manually
Thanks...I'll test this out when I get the RX back and see if I see the interior or dash lights doing something unexpected with regard to the doors.
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Old 10-30-12, 10:08 AM
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Had the same problem on my 2010 RX hybrid. It only occurred while on vacation and parked outside in Florida. I thought it was heat related but after reading this, I guess not. It never occurred while in Kentucky or parked in the garage. Hasn't happened in over a year. Weird.
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Old 10-30-12, 09:46 PM
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Originally Posted by DunWkg View Post
RXSF, does your problem occur day or night? Does it occur immediately adjacent to, but not in the garage? What's powered up in the garage? Refrigerator/freezer/furnace? Probably not a furnace in SanFran.
It only occurs when I park in the garage (single space). I have a refrigerator in there, washer, dryer, and also my home alarm system which I suspect is the cause of all this.

I have had my old RX alarm go off in the middle of the night without me knowing and by morning the battery was dead.

It doesnt matter night or day, just whenever I have it locked and parked for a few hours
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