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Alarm siren sounding randomly?

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171K views 122 replies 63 participants last post by  cloves  
S
#1 ·
Based on suggestions from other forum members I have finally fixed my siren. I thought I'd show how I did it so anybody else could do something similar if they wanted to.

Basically, the siren will sound on its own when the internal batteries drain below a certain level (seems to take around five years). A new siren will cost almost £200 so that's a no-no for most. The batteries are unfortunately not available in the UK or Europe. There are similar batteries available, but they are NOT the same and will cause problems fairly quickly.

I have now fitted an external battery box using CR123A photographic batteries which have similar characteristics to the original spec batteries. They are easy to get hold of anywhere.

The parts used are as follows. From RapidOnline: IP65 rated box (ABS Clear 65x60x40), CR123A battery holder. From Maplin: switch (type E - which was all they had in stock which was suitable), waterproof switch cover. I also used some twin-core cable suitable for automotive use (hot/cold resistant) and automotive silicone sealant. (A switch isn't actually necessary, but I wanted to be able to disconnect the batteries instantly, just in case.)

The box itself cannot be too big or you will not be able to pass it through the hole in the wing. If in doubt, try it first. Make sure the box is waterproof. If it states IP65 rating then it should be fine.

If anybody needs just the CR123A battery holders then PM me as I bought a load (well, 30) as they were so cheap compared to their standard delivery charge.

If you need to see how to get to the siren and take it apart see here for the instructions I originally used.

The original orange CR17335 batteries (on the left), CR17335SE batteries (fitted) which DON'T work and some CR14335BL batteries which did work for a while.
Image


You'll need some form of soldering tools (soldering iron and, if possible, a desoldering tool).
Image


Here's the siren taken apart, showing the cable soldered onto the positive (lower left) and negative terminals on the underside of the circuit board. I made sure the cable wouldn't snag or be squashed by routing it around one of the sirens. I drilled a hole in the bottom of the siren and once everything was in place I sealed the hole with silicone sealant.
Image


The siren with the circuitboard in place. Make sure you replace the (circled) jumper on the circuitboard if you removed it.
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I drilled two holes in the side of the box, one for the switch and one for the cable. The switch has a waterproof cover and the cable was sealed with silicone sealant.

I soldered leads to the battery-holders so they are in series and then to the switch fitted in the side of the box. Positive on switch to positive on battery one, negative on battery one to positive on battery two, negative on battery two to negative on switch. Take care with this and double check the polarity as you don't want to get this wrong. Then solder positive to positive (and negative to negative obviously) in the cable from the siren to the switch.

The picture shows how I 'glued' the battery-holders to the base of the box using the silicone sealant and being held by a clamp.
Image


The finished box with batteries in place.
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The finished article. The cable is approx 40-50cm in length to allow the box to be passed through the hole in the inside wing from the wheel-arch side (a helper is useful for this) before fitting the siren back in its place in the wing.
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Lastly, I fixed the box using outside sticky fixers (having cleaned the surfaces first). It just tucked nicely under an earthing cable for a bit of extra support. I've marked the cable which goes to the siren in red.
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That's it. Enjoy the silence, but also the knowledge that if someone does tamper with your pride and joy, the siren should sound.
 
C
#6 ·
Hi guys,

I have seen a couple of threads on this subject of the alarm going off randomly on Saabs - could this also apply to the 9-3 range also, as I am experiencing a similar problem on a 2001 Y reg Saab 9-3 Turbo 3dr hatch.

The alarm seems to be going off randomly when the car is remote locked (deadlocked or not - makes no difference).

When I first bought the car the battery was flat as a pancake and the alarm was going off every 15 mins or so once we got the car running and the batt had a bit of charge in it.

I charged the car battery up fully over a day with a batt charger when I got the car home, and it has been ok for a week or so, but now the alarm is starting to go off when it feels like it again.

I am not getting any messages about the theft alarm system on the SID though...
 
#7 ·
Welcome :)

Yes it does also apply to the 9-3, which has the same basic system and siren. The other parts that I have known give trouble on the 9-3 are the tilt and glass break sensors. Press the Night Panel button just before exiting the car to disable these- the SID should say "door alarm only" or something similar. If the alarm still goes off then it's almost certain to be the siren.
 
C
#8 ·
Hi Mark,

Thank you for your advice - I suspected that they would be similar, as my symptoms seemed to match those listed here.

I did try the night panel trick once at work, and I think that the alarm still went off - although by the time i got to the window to have a look, the alarm had gone off, so I dont know for certain.

I read also a faulty tilt sensor might cause a similar problem? - do you know where I would find this?

Thanks again,

Cheers,

Coop
 
S
#12 ·
A few weeks after I posted the battery fix for the alarm my siren went off again, but having checked and changed the batteries (having found one to be slightly low for some reason - possibly faulty) I had no problems again.

A few weeks ago, during some cold nights, the siren went off a couple of times again ( :mad: ). It then got much worse, so I decided to investigate further (after disconnecting the batteries with the switch and removing fuse 14 to ensure temporary silence). The batteries were fine so I decided to check out this SaabCentral link (as provided by yeldarb here - thanks for that). It seems that one or more of the three electrolytic capacitors can break down with age (possibly made worse when cold) giving rise to the 'Service Theft Alarm' and random siren activation problem in the same way failing batteries can. This only seems to happen to some, so maybe I've been unlucky. The failing battery will (eventually) happen to all.

I have now replaced the three electrolytic capacitors on the circuit board and all is well again (despite some more cold nights) :thumbsup:!

If anybody is going to do the siren batteries then I'd strongly suggest replacing the capacitors too (while you're in there anyway). They are very cheap and easy to fit. I got mine from Rapid Online (see here - order codes 11-1541, 11-1554 and 11-1559). The Voltages are slightly higher on two of them as I couldn't get exactly the same (perfectly OK), but the capacity is the same (more important). It is OK, according to the SaabCentral link, to up the capacity by up to 50%, but I cannot vouch for that as far as the siren goes. Upping the Voltage by double or even more is OK, but never replace it with a lower Voltage capacitor. Higher Voltage means slightly more expensive (but they are only pennies anyway) and larger size, that's all. I bought ten of each so have some spares if anybody needs them (as well as the battery holders). Just send me a PM.

Here's what I did.

The three capacitors which need replacing while still fitted to the board (C1, C2 and C4 - C3 is a different type of capacitor). Note the stripe down one side of the capacitors. This signifies the negative side and it is VERY important they are replaced the same way. You risk them blowing up if put in the wrong way.
Image


Here they are once removed. All three are high temperature 105 deg C capacitors (which my local Maplins didn't have in stock, but Rapid came to the rescue).
Image


To aid removal a desoldering tool is very useful (see the second pic at the very top of the thread showing the board, a soldering iron and the desoldering tool).
Desolder the capacitors from the board as shown below (two have already been fitted with one to go). The big capacitor (C4) needed a bit of help to get it off as the base of it is stuck to the board. Levering with a screwdriver did the trick. That would be much more difficult if I hadn't removed all the solder with the desoldering tool.
Image


New capacitors fitted. I had to fit the big (and taller than the old) capacitor on its side (good job the alarm batteries weren't in the way) as I wouldn't be able to fit the lid otherwise. I fixed the big one to the board with some silicone sealant as otherwise vibration might be a problem in the future. I added some sealant to the base of the other two for the same reason.
Image


Hopefully doing this will finally provide a working alarm which only goes off when it's supposed to (and here's hoping that it won't do so).
 
S
#15 ·
Befroe fiddling with the electronics, it would be worth asking your freindly mechanic to check the bonnet switch. That turned out to be the cause of my 9-5's alarm going off three times one evening.[/b]
Click to expand...
Presumably that set the alarm of 'properly', with siren going and indicators flashing. The problem with the batteries (and/or capacitors) going is that the siren goes off by itself, i.e. the alarm itself is not going off with flashing indicators etc., it's just the siren blaring away annoying you and the neighbours with no way of turning it off.

Glad you got yours sorted though.
 
#16 ·
Seems to me there's a potential small business opportunity here.

I have the random siren problem with the result I'm now locking the car manually. I have virtually no electro-mech experience nor, quite honestly, do I have any interest in doing these things myself. I don't expect that any of the Saab specialists are interested either, however if the problem is as widespread, or potentially widespread as it might seem, then maybe the specialists might be interested in buying ready modified units for a swap-out service. If it really is a 30 minute job to upgrade the siren units in this way, then selling a modded unit for £50 might be some worthwhile pocket money.

And I'd certainly be willing to buy a modded unit and ask a specialist to fit it for me.

Anyone want to supply me one?

Keith
 
S
#17 ·
I fitted my upgraded back up unit as built by someone not a million miles away today!

I can thouroughly recommend him. There is potential for him to make a bit of money.

As for fitting....I had to take the wheel off,undo the screws on the arch liner and fiddle

about a bit.........If I can do it though!!! Anybody can!!

I would expect that you will get a PM or two Gassy!!
 
M
#18 ·
Hi,

I'd also like to add my two pence worth.
Before even purchasing batteries as my old and current one still read 3+ volts go for the capacitor change. I did my batteries (like for like) a year and a half ago and all was well but issue re occured.

So I've gone dowm the 70p fix being the capacitors it's been well over a month and all is good...
I found my post here, which is more of the same above.
 
P
#19 ·
Hi,

Is your alarm still working fine after the capacitor change? I did change all of three caps, it works ok for almost one month, now it starts sounding randomly again!! There must be something else wrong with this alarm system. In my case, I measured 3.1V on both original battery and I thought it should be alright, so I did not replace the battery. On my SID, no "service anti-theft alram" message ever showed. Do I have to replace the battery?

Jason
 
S
#20 ·
Is your alarm still working fine after the capacitor change? I did change all of three caps, it works ok for almost one month, now it starts sounding randomly again!! There must be something else wrong with this alarm system. In my case, I measured 3.1V on both original battery and I thought it should be alright, so I did not replace the battery. On my SID, no "service anti-theft alram" message ever showed. Do I have to replace the battery?[/b]
Click to expand...
I'd guess the battery is on its last legs and should be replaced. If it's still the original battery in there then it will be quite old by now. The trouble with Lithium batteries is that they are difficult to measure with a multimeter. The Voltage tends to stay at normal levels right to the end of its life. 'Normal' batteries, like 1.5V alkalines gradually drop their Voltage until it's too low to work.

I've had no problems at all with the external battery and new capacitors fitted.
 
#22 ·
My '54 (Jan 05) Vector's alarm has gone off - with flashing lights - about 5 times in the past year, always during the night when it's pouring down and also a bit windy (mildly squally?).

Having read this post before, I don't think it'll be the battery failing yet, and the flashing lights also discount the battery issue. It did it again last night, so I thought I'd ask if anyone has any thoughts or comments?
 
#24 ·
Hi CitTone, that's a good question well put. I dunno. My Xantia was well behaved in the alarm department. Unlike its spheres (VSX). You've changed your picture?

I thought it might be an oversensitive volumetric thing, but it wasn't actually windy enough to really rock the car around. Anyone got any other experience of oversensitivity?
 
N
#26 ·
My '54 (Jan 05) Vector's alarm has gone off - with flashing lights - about 5 times in the past year, always during the night when it's pouring down and also a bit windy (mildly squally?).

Having read this post before, I don't think it'll be the battery failing yet, and the flashing lights also discount the battery issue. It did it again last night, so I thought I'd ask if anyone has any thoughts or comments?[/b]
Click to expand...
It'll be the glass-break sensor I'd have thought. Saab alarms commonly go off in heavy rain / hail for that reason.
 
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