Can a cell phone set off a car alarm?

We have a 2004 Toyota with a factory installed car alarm. The alarm goes off randomly. Sometimes a few times a day, some days not at all. No physical disturbance is setting it off (it does it even sitting in our closed garage). However, we noticed that it seems to happen when my daughter's cell phone is in the car. I am still trying to confirm this relationship (by having the phone in there, or not having it in there, and seeing when the alarm goes off).

Could the cell phone be setting off the alarm? It's nothing obvious, like the phone being on "vibrate" mode, and receiving a call. Could the phone be sending a radio signal that is at a frequency that sets off the alarm (like the frequency of the emergency button on the key pad)?

We had it at the Toyota dealer, but they didn't find anything (this was before I made the cellphone connection).

Thanks for any help!

DanK

Reply to
DanK
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It will be difficult for a dealer to test for this, as they are not equipped to do EMC testing. Phones do send out a "call home" signal periodically which could be affecting the alarm. A phone will increase the strength of its transmit signal, in badly covered areas so it can be received by the network.Possibly increasing the chance of interfering with the car alarm.

A bad case is here:

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martin

Reply to
martin griffith

To check the phone, you can buy gadgets that light up attached to the phone. You will know anytime the phone transmits. Try malls or cellphoneshop.com

greg

Reply to
GregS

Yes. Cell phones periodically transmit their location to the tower even when you're not using them, so the tower will know where they are.

Some audio systems and radios will also pick up noise from the cell phone when it's doing this. You may be able to use a radio as an indication of when it's doing it.

Reply to
mc

Call the phone in the car - see if the alarm goes off. Field strengths of a GSM at full power in a semi-closed metal cabinet may be > 10V/m.

--
 - René
Reply to
René

My car windows occasionally opened by themselves, and once the moonroof opened by itself as well. I stopped carrying the remote in my pocket - that solved the problem! I was pressing buttons when I sat down, etc, and holding certain ones down caused the windows to go up and down.

Mark

Reply to
Mark X

[snip]

I kept having that problem at home, the only place where I was within range while seated.

I kept opening the trunk, which turned on the trunk light, which killed the battery a few times.

I solved the problem by removing the rubber diaphragm from the remote and cutting off the "nubbin" under the trunk position so that, when reassembled, to open the trunk required putting your finger down in a hole ;-)

(Locking/unlocking doors, etc., was no problem, since the car is garaged. Likewise, interior lights time out, but trunk light doesn't)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

I would be lying down or bumping agaist something and my truck would start. My truck, a Dodge Dakota, louder than most, can easily be heard indoors.

I have heard of car running problems when passing the outside TV/FM tower with another 80 services running on it. Equipment in windows in view of the tower often didn't function well.

greg

Reply to
GregS

Alarm systems use fairly long code sequences for security reasons. They also have their own assigned frequencies. This makes the cell phone an unlikely candidate.

More likey, if somewhat paranoid, is someone with whats called a 'scanner' trying to break into cars in you neighborhood. These units generate all possible codes to help in stealing cars.

Luhan

Reply to
Luhan

Yes.

No it's probably not that. If it is the phone the signals are probably getting into the alarm system via pickup in the sensor wires or via the alarms power cables. You've probably heard the noise they can produce on PA systems and radios. It might be worth checking that all the connections to the car battery are tight and in good order.

If it's not that then you need to find a local electronics expert or perhaps a ham radio guy to help locate the problem.

Reply to
CWatters

And try it in more than one position in the car. Signal strengths vary depending on the orientation of the car and the position of the phone inside the car. If that's the case it's probably sneaking in through unshielded wires behind the plastic dashboard or something along those lines.

If you've ever left your cell phone on top of one of those old- fashioned (Braun) tube type computer monitors and it rang, you know there's a *lot* of interference that comes off a cellphone under some conditions.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Reply to
Spehro Pefhany

I have the same exact problem with my Saturn remote bumping against anything in my pocket.Sets off the alarm.

In the newspaper some years ago, a whole family died from Monoxide when a car was running in the garage while they slept. Police said there was no evidence that suicide was involved. I wondered about those "remote car starters", which, like the remote for my Saturn, has no "ridge" around each keypad to prevent a coin or whatever in my pocket from activing the remote.

About all we could do is glue a thick grommet aroung each pad.

I wonder if that family died because of that. A veeeery bad design.

Best-- Ron

Reply to
Ron Gould
["Followup-To:" header set to sci.electronics.design.] On Mon, 22 May 2006 18:16:09 GMT, GregS wrote in Msg.

Good thing you didn't park it with first gear in and without handbrake like I do.

robert

Reply to
Robert Latest
["Followup-To:" header set to sci.electronics.design.] On Mon, 22 May 2006 23:22:07 -0500, Ron Gould wrote in Msg.

Or disconnect the battery when the car is parked. It seems that as technology progesses, we need more and more such brute-force solutions to problems that didn't exist before.

Like my wireless phone at home: At night I switch off the base station because I don't need it. When I first started doing that I noticed that the batteries of the handset, which normally last a couple of weeks, run flat within one night. Apparently, by virtue of some braindead Philips design, the handset keeps transmitting full power as soon as it loses contact with the base station. So I remove the handset's batteries as well. At first I was annoyed that now, each morning when I put the batteries back in, the phone clock starts at Jan 1 00:00:00 2004 but I got used to that.

Ten years ago we had telephones that used no power at all when not in use.

robert

Reply to
Robert Latest

I knew this would be a problem when I first saw that fob, so the fob never goes in the pocket- was stopped by a policeman once about that "knife" I was carrying around- turned out he was a knife collector. Then there are others who apparently think it is some kind of sexual gesture.

Reply to
Fred Bloggs

They don't start unless they are in park. They also shut off after 7 minuites. Manuals require an unengagedl sensor.

greg

Reply to
GregS

[snip]

Strikes me that remote starting is a very bad idea.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Fred, Ehhh? Not quite coherent yet this morning ?:-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Ever since I've heard of such a thing, whether in a car or in an emergency standby genset, I've wondered, "How does the remote starter know when to stop cranking?"

Thanks, Rich

Reply to
Rich Grise

Don't they have any building standards? Our garage has a mandated automatic door closer, gasket seal, fire door, and a solid concrete wall between garage and living space. Nothing's getting through there.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Reply to
Spehro Pefhany

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