I went through 2 siren units within 21 years, so I guess the 3rd one will probably outlast the car. Can't separate without cutting it and even after, all are soldered.

Given all the circuitry inside i don't think they're interchangeable with newer units, but if they are,would be very nice!

 

Looking like a non-starter. WDS shows the E60 / E90 era alarm sirens have only 3 terminals whereas our era sirens have 4. Shame. The connectors had looked similar when I first looked at ebay listing photos but they were all underexposed, and when I boosted the shadows in Lightroom then, sure enough, only 3 pins.

Oh well. As you were, everyone.

 

E46

E90

Connectors are the same, regardless of the amount of pins, but activation on KCAN cars is (obviously) via KCAN, which I'd imagine won't have the same message structure as KBUS.
I thought you were thinking of replacing specifically the battery unit, not the whole siren? It may be easier/doable (provided voltages match up).
Looking at the photos of the cell pack reminds me of the flashlight battery, cumbersome but ultimately replaceable.

 

Ah, I'd overlooked the later cars are DCAN compared to our K-bus. Even less chance it would work. I've now abandoned that idea.

Instead I think I'll pick up a used E46-era siren to practice cutting open (they're only £10 used here). There is someone selling the cell packs on ebay for £20 if I can manage that without destroying it:
BMW 3/5 Series Car Siren Alarm Battery Pack E38 E39 E46 E53 E83 M3 M5 X5 | eBay

Failing that I'll have to buy new. (And if I did I'd get a US-spec version - much more chance of hearing that going off than the ECE version!)

 

Didn't even know about this... I guess this explains why my battery was flat, after I let my car sit for a few weeks.

 

if you enable the chirp on arm/disarm, and listen at a quiet location, you can hear when the battery is weak, and when it is strong.

i think best way to access batteries would be a vibrational flush cut tool. you'll go through a lot of blades, but it will be clean, and you can later turn the cutout piece into a hatch. when you cut, use the corner of the blade and follow your cutline. don't lay the cutting edge level, or you'll have no control.

 

if you enable the chirp on arm/disarm, and listen at a quiet location, you can hear when the battery is weak, and when it is strong.

i think best way to access batteries would be a vibrational flush cut tool. you'll go through a lot of blades, but it will be clean, and you can later turn the cutout piece into a hatch. when you cut, use the corner of the blade and follow your cutline. don't lay the cutting edge level, or you'll have no control.

I do have audible arming acknowledgement coded on but I'm UK so have the quiet beep ECE alarm rather than your loud wail US alarm. It doesn't chirp on lock but beeps once. Best way for me to test the siren battery is to disconnect the car battery with the alarm armed. I only get about 2 seconds' worth of beeping - 2 beeps - before it dies.

Thanks for the tip about those flush cutting tools. I've found they're called "oscillating multi-tools" here and they look useful for all kinds of things.

 

"oscillating multi-tool" is the official name of these things. the patent expired only recently, which is why we waited so long for such a simple device to become commonplace and affordable. the blades are a ripoff though. go slow and never let them get hot. i swap blades every minute or two , so i can keep working without waiting.

thanks for cutting yours open for us. i'll definitely be copying your successful cutline to open my siren. just tried your disconnected battery method, and i got about 30 seconds before it went weak then slowly died.

 

I just gotta give some love to @paraklas , he’s a real gem on here. So many cool fixes/mods done and always freely shared information. Thank you, sir!

 

Well thank you @Bali appreciate the nice comment!!! If it wasn't for the community here I probably would had sold my E46 many years ago..

Ps; I opened that siren with a hammer, pieces flew and spread around my garden and then realized maybe I should take a photo for someone might need a battery replacement, so I got the pieces back together

 

hammer is the universal tool. i took out my siren yesterday to see what all the fuss was about, and it is indeed impossible to pry open. as i remembered, there are two screws at the back, which fool us into thinking the halves separate, but NO. what are those screws even for, except to troll us?

 

what are those screws even for, except to troll us?

BMW engineers have trolled us in other ways too. We recently started a list…

Questionable Design Decisions

Starting a list of head scratching aspects of the E46 that make you ask yourself, WTF were they thinking? This is meant to be fun and educational, not bashing. See the curated lists from all posts below. ENGINE CCV system molded DISA seal plastic valve cover MS42 hybrid throttle control weaker...

www.e46fanatics.com

 

if you can cut the flap cleanly, then just glue a slightly larger thin piece of plastic over it - to keep it from falling in. then either glue the flap down with silicone, or better yet cut a custom gasket, and screw the flap down.

 

btw, unless you buy them prewired, you'll need a spot welder to string the coin cells together. you can also buy individual cells with tabs included. unless you have access to a spot weld tool, make sure you buy the kind with prewelded tabs.

 

Thanks. I'd be buying them from my link in post #6.

I'm hoping that connector on them I've circled is the same as on the originals and just plugs in. That over-exposed pic is the only one on the listing.

 

you could have bought any 7.2v NiMH pack that fit the empty space available. worst case i could have welded together the same configuration you ordered. cancel if you can. that's too much money after shipping.

if you could make this fit, the alarm could run for months without draining the car battery. may even be worth expanding the siren housing for the upgrade.

 

you could have bought any 7.2v NimH pack that fit the empty space available. worst case i could have welded together the same configuration you ordered. cancel if you can. that's too much money after shipping.

Aha. I've not ordered yet so still time to DIY if that's an option. I did think £20 was cheeky for £1 worth of cells but was then thinking if they've been spot welded and had the correct connector put on it'd save me a lot of fiddly work I would probably struggle with. Including his time to do that it didn't seem too unreasonable. I'm UK so shipping to me is free.

 

i spot weld cells with the car battery and rubber washing up gloves on. works a treat for coin cells. definitely DIY it. you can reuse the connector on the spent battery pack.

 

Interesting! You know, I might try just try that first. What have I got to lose?

:goes off to find some tutorials:

Cheers!

 

it isn't rocket science. just be careful and don't die. everyone would blame me for leading you to danger.

 

And, in case anyone is wondering why I don't just remove the siren since no-one's going to try stealing an worthless old E46 with EWS when new £100k Range Rovers can be stolen with an ipad, it's for the alert it gives the car's being jacked up. Catalytic converter theft is a problem here. My sister had hers taken from her year 2000 Mazda when she visited a few months ago. Parked outside the house, 1pm on a sunny Saturday, and within 5 minutes of her coming in the house they'd pulled up alongside it, jumped out, jacked up her car and sawzall-ed it off. All whilst the neighbours across the road were unloaded their groceries and the postman walked by. Caught on security cameras but we had no idea until she went to go home and started the car to find it was now straight-piped. If we'd looked out the front window we'd have seen them at it, but we were all in the back garden enjoying the sunshine. if she'd had an alarm that went off like ours does when the car's being jacked up we'd have been on them or they'd have driven off. (I know in the States you don't have converters under the car but we do here, and they're £1000 plus labour to replace.)

 

We do have converters here and their theft is a growing problem.

 

Yours are in a different place on the E46 though, from what I understand from this forum

 

Update. Received a used alarm today and carefully cut it open.

@Bali was spot on in this thread when he said the cells leak:

OEM alarm draining battery?

The connector were the battery plugs on to the board was destroyed. It had gone yellow and crumbly, like honeycomb in water. I've cleaned everything up with vinegar and a toothbrush but I don't know if it's worth putting a new battery in or whether the PCB circuitry will be ruined.

Which made me think. Does the alarm need a battery for normal operations? I know it'd need its own power source to keep working if the car battery is disconnected, but I only care about it working when the car's being jacked up whilst parked, when they haven't got in the trunk to disconnect the battery. Maybe if I cut my own alarm open my battery won't have leaked, and I could just take the battery out before it does. I don't suppose anybody knows but I might try it and find out.

Edit - Funny how typing something out makes the next step more obvious. I need to screw the potentially leak-damaged ebay alarm back together (won't bother sealing it) without a battery in it and see if that works in the car. If it does, it tells me that the circuitry isn't ruined and also that the alarm doesn't need a battery for normal ops. If it doesn't work then I need to open mine up and remove the battery. I know that one works when the car battery is on so its internal circuitry must be OK.

 

Confirmed alarm does still work without cells installed (as long as car battery is connected, of course).

I think this is actually a better solution for me than replacing the cells. It's evident these cells have a limited service life. New replacements would also go bad in time. Deleting the cells entirely means no parasitic draw again in another few years, no leaking all over the circuit board again. I still have a working alarm with a tilt sensor against catalytic converter theft, and an ultrasonic sensor against someone gaining entry to grab what they think is my phone. I'd recommend everyone with a factory (dealer-fitted in the States) alarm considers doing this. Do the car battery disconnect when armed test, if it fails that your cells are bad.

This was my cell deletion process:

- I found it cleanest to cut open (I did two, with different methods) using a junior hacksaw. I gripped it in a soft-jaw vice and worked my way around. Just go as deep as you have to, so you don't risk nicking the two wires going from the circuit board to the sounder. Don't forget to remove the screws.

- Separate the two halves by pulling them straight apart, not opening like a book. The connector has four pins that can bend otherwise, meaning the car harness plug won't go back on without a lot of effort to make them exactly straight again.

- Disconnect the battery of dead cells form the board and remove it from the housing for environmentally responsible disposal. On one I did the cells had leaked, on the other they hadn't. On the one that had leaked, I swabbed the circuit board with vinegar to neutralise the spilt alkaline, rinsed and dried overnight in the airing cupboard. On the other, I went straight to the next step.

- I applied a continuous thin bead of adhesive silicone sealant around one half of the unit, put the two halves together carefully, making sure the four connector pins went through the other half cleanly. Reinstalled the three screws to clamp together. I also ran a length of waterproof(ish) tape around the seam afterwards, but this was probably overkill. The unit sits under the rain guard that houses the microfilter, which should by a dry location.

- Reinstall in car and tested by locking/arming with the key centre button (ie as normal) then unlocking by turning the key in the door lock and opening the door. Alarm sounded successfully.