Frequent false alarms

[Jon_G]

Over the years we've suffered practically no false vehicle alarms on our soft top model... those we have had were usually explained by the wind or a cat. However in the last year or so we have suffered the odd unexplained alarm which has become more frequent. Last night the alarm went off in the small hours, was reset... went off again, so the car was left unlocked.

We always park the car and then push the 'lock' button twice.

I've had a look this morning and all doors, boot and bonnet were properly shut, plus (despite the surrounding mud) no signs of a cat having been on the car. And it wasn't very windy here last night.

We bought the car new from a UK Toyota dealer, so I know the alarm is standard and hasn't been played with over the years (I did once remove it, while replacing the radiator, but it went back in exactly as it came out).

I just did a forum search on 'alarm' and studied the first 10 pages of results, but nothing relating to this problem that I could see. So, is there a common reason for this (a door, bonnet or 'boot' switch, maybe)? Or should I expose the unit under the bins and turn the sensitivity down? Or something else?

[Joesson]

I suggest that if it where any switch at fault then the alarm would not set, so that would leave the sensitivity control.
In my experience alarms do go off in the small hours.
I awoke to what I thought was the house alarm. After resetting it the house alarm went off.
This was when I realised it was the smoke alarm that had woken me!
(This turned out to be a low stand by  battery and so the mains power had sounded the alarm)

[Wabbitkilla]

How old is the battery?

[stewart@boro]

Had a few false alarms, central locking and some starting problems 6 months after I bought the car(before been a member here).
Replaced the battery and not had a problem since(electrical that is  s:wink: :wink: s:wink:  )

[Jon_G]

How old is the battery?

It's only about 2 years old... it was a genuine Toyota replacement (from CTP). Seems perfectly OK regarding starting, etc.

[Wabbitkilla]

Sounds (to me) like your battery is getting tired .... this happens quite a bit and the colder the weather the worse it will get.

[1979scotte]

How old is the battery?

+1 dying battery causes issues

[Jon_G]

I'm certain it isn't the battery... as said, it isn't very old. And I'm not seeing any signs that the alternator isn't keeping it fully charged.

[Thehazzle]

Been happening to mine today too maybe best to get new battery before winter fully hits

[Joesson]

But the OE's battery is only   two years old!
My 2 battery, a Unipart, fitted by the previous owner is five years old.
My car has been standing since the end of October with a trickle charge a couple of weeks ago and it started the car first go yesterday!
My other car battery is two months short of four years old. Its a diesel car and starts easily to date.
Two years for a modern battery is not even out of warranty, I can' t understand how a battery that has the power to start a car does not have the power to maintain an alarm circuit!
Trying an adjustment should not break something that is already in some way broken!

[Wabbitkilla]

That's fine just ignore people who have experienced the problem and carry on regardless. Or take the battery off, give it a good charge in the home, refit it and see if it settles down for a while. Dying batteries die quicker in the cold

[Jon_G]

But the OE's battery is only   two years old!
My 2 battery, a Unipart, fitted by the previous owner is five years old.
My car has been standing since the end of October with a trickle charge a couple of weeks ago and it started the car first go yesterday!
My other car battery is two months short of four years old. Its a diesel car and starts easily to date.
Two years for a modern battery is not even out of warranty, I can' t understand how a battery that has the power to start a car does not have the power to maintain an alarm circuit!
Trying an adjustment should not break something that is already in some way broken!

Thanks. The original battery actually lasted an impressive 9 years, although during its last year it was obviously struggling. But even towards the last few months of its life (when the terminal voltage was less than 12.2V after standing overnight) we never had a problem with the alarm.

Let me be clear in case there are crossed wires with so many posts telling me it's the battery, despite me saying it's only 2 years old... when I say 'battery', I mean the main car battery. Are people trying to tell me it's the battery in the actual alarm? Apologies if I've misunderstood!

[Jon_G]

That's fine just ignore people who have experienced the problem and carry on regardless. Or take the battery off, give it a good charge in the home, refit it and see if it settles down for a while. Dying batteries die quicker in the cold

I'm not ignoring you!

But it isn't the battery... the battery isn't very old. Yesterday the car did over 200 miles so the battery got a good charge (alternator putting out 14.4V at 1500 RPM, even with headlights and HRW on).

[Bernie]

Might be worth checking out the microwave sensor info here

  l viewtopic.php?f=31&t=19607&p=242251&hilit=Alarm+sensor+adjustment#p242251 l

[Jon_G]

I suggest that if it where any switch at fault then the alarm would not set, so that would leave the sensitivity control.
In my experience alarms do go off in the small hours.
I awoke to what I thought was the house alarm. After resetting it the house alarm went off.
This was when I realised it was the smoke alarm that had woken me!
(This turned out to be a low stand by  battery and so the mains power had sounded the alarm)

Good point about the switches. I can see that the door switches are OK (interior light comes on and off reliably) but I was concerned about the other two, as I am not aware of an alternate function for those as a test. I'll focus on checking (and maybe adjusting) the sensitivity first, then if that seems OK I'll access the switches to check the contact resistance.

Might be worth checking out the microwave sensor info here

  l viewtopic.php?f=31&t=19607&p=242251&hilit=Alarm+sensor+adjustment#p242251 l

Thanks very much for that... tomorrow I'll work towards whether I need to access the sensitivity control and also consider what might be a reasonable change to make.

[Jon_G]

Please could someone confirm which battery it is that can sometimes cause the alarm to randomly trigger?

If it is the one internal to the alarm is it easy to obtain and replace?

[Wabbitkilla]

Not the internal alarm battery, the cars main battery.
Worth checking the voltage in the morning before you start it just for curiosity.

[Jon_G]

Not the internal alarm battery, the cars main battery.
Worth checking the voltage in the morning before you start it just for curiosity.

I will do that first!

Thanks.

[Jon_G]

Not the internal alarm battery, the cars main battery.
Worth checking the voltage in the morning before you start it just for curiosity.

OK, so I've just checked the battery voltage and it's 12.49V... so not too bad considering it's only 3 degrees C up here at almost 1,100' ASL and the car has been standing since late Wednesday afternoon. It's an old multimeter with uncertain accuracy but, for comparison, my Honda Accord diesel is showing 12.47V and has an even newer battery. I admit I would have expected to see 12.5V minimum on both, but that is maybe idealistic.

I'll not be doing much else to the car today as I don't have a garage and the high wind chill is making outdoor work a little unattractive here today. But I will have to tackle the problem over the weekend!

I will post an update when I have something interesting to report.

[Jon_G]

After measuring the battery voltage this morning, I locked the car by pushing the remote 'lock' button 3 times to operate the deadlocks but disable the movement sensor. I carefully witnessed the vehicle responses, so know that these 3 signals were received.

However, just a short time ago the alarm went off! So what other factors lead to the vehicle alarm sounding... must this recent alarm be due to a door, bonnet or boot switch fault, or are there other alarm inputs?

[mrzwei]

Different car so I just offer this for what it's worth.
Saab alarm has a supposed lifetime internal battery but it  can start to fail after about seven years. Symptom is random alarm activation, cure is replacement internal battery.
The system is well sealed and the oem battery is no longer available. Solution costs 40 quid at a specialist.

If all else fails then that may be an issue although I would have expected the problem to be more widespread.

Also, lots of historical posts on here about baby alarms etc. new to the area causing frequency issues. The taxis parked in Tescos car park could set off my old Z3 alarm with their comms system.

[Jon_G]

Different car so I just offer this for what it's worth.
Saab alarm has a supposed lifetime internal battery but it  can start to fail after about seven years. Symptom is random alarm activation, cure is replacement internal battery.
The system is well sealed and the oem battery is no longer available. Solution costs 40 quid at a specialist.

If all else fails then that may be an issue although I would have expected the problem to be more widespread.

Also, lots of historical posts on here about baby alarms etc. new to the area causing frequency issues. The taxis parked in Tescos car park could set off my old Z3 alarm with their comms system.

Thanks. As you say, you'd expect this problem to be more widespread throughout the forum if the internal battery failing caused this problem on our cars... but maybe I've been unlucky! And I should think that most of the original internal batteries are now dead or dying anyway?

I'll concentrate on checking out the door, bonnet and boot switches today (lift the caps and spray in switch-cleaner) and then see how it goes.

[Jon_G]

I'm still struggling to sort this problem out.

To make the car able to be parked quietly when away from home I've removed the alarm sounder from under the spare wheel. But the alarm is still active and still false alarms (via the indicator lamps) within about 30 - 300 seconds of the alarm being set (e.g. 2 pushes of the remote 'lock' button). So we are now just pushing the button once, which seems to avoid us making a nuisance of ourselves in car parks, etc..

Before removing the sounder I tried to assess whether the movement sensor was actually too sensitive by setting the alarm with a window open, waiting a while, then sticking my arm/head/body into the cabin to see how sensitive the movement sensor is. And it turns out that it isn't sensitive at all! So I now think the unit with the sensitivity control is at fault... has anyone else had to repair this unit? Any circuit diagrams available?

[Joesson]

I know that to reset the EMS the battery should be disconnected temporarily.
When this is done the car makes a beeping noise.
Would disconnecting and then reconnecting the main battery not only reset the EMS but also the alarm?

[Jon_G]

I know that to reset the EMS the battery should be disconnected temporarily.
When this is done the car makes a beeping noise.
Would disconnecting and then reconnecting the main battery not only reset the EMS but also the alarm?

Is the EMS another name for the engine ECU?

I've never heard our's beeping when disconnecting the car battery but maybe I didn't notice, as I tend to have a radio on quite loud when working on cars. And the battery has only ever been disconnected once since the car was new!

I assume that the vehicle alarm controller has it's own internal battery (like the sounder under the spare wheel), so disconnecting the car battery would have no effect... but I could be wrong! I will do a 30 minute disconnect and see if that helps.

Annoyingly, while I have a very comprehensive workshop manual DVD, there is no detail of the vehicle alarm system - maybe because this was fitted by the UK dealer who sold the vehicle (I understand they were shipped from Japan without an alarm)?

Thanks.