Does anyone have one of these Hella 5aa 003 525-00 Alarms fitted to their car or know anything about how they work?

I have looked on Wiki and checked a couple of manuals but I cannot find any information on them or what they do?

If anyone has one and any advice on how to check it I would be most grateful

Morning Paul

Wow that stirs the old grey matter

I take it your familiar with www.realoem.com check the Classic section or BMW have a Classic section try their Customer services (I am told they can be slow)

If I recall alarms were not a standard fitting back then so you may find Baur fitted it when they retrimmed the car

Maybe a question to Baur in Stuttgart I am sure they will have an Archive

Good Luck

Dave

I agree with Dave, back in the day most alarms were retrofit and Hella being an independent company supplying electrical relays and associated switches to fit to Baur and other styling houses of the era.
I would be tempted to track the wires individually to see where they go to - I would imagine one or two would go to the starter motor and ignition switch / coil, etc

Let us know how you get on with it all

5 hours ago, Greydog said:

Morning Paul

Wow that stirs the old grey matter

I take it your familiar with www.realoem.com check the Classic section or BMW have a Classic section try their Customer services (I am told they can be slow)

If I recall alarms were not a standard fitting back then so you may find Baur fitted it when they retrimmed the car

Maybe a question to Baur in Stuttgart I am sure they will have an Archive

Good Luck

Dave

Thanks Dave I will recheck my realoem and the classics section just in case I missed something

3 hours ago, BOC Admin said:

I agree with Dave, back in the day most alarms were retrofit and Hella being an independent company supplying electrical relays and associated switches to fit to Baur and other styling houses of the era.
I would be tempted to track the wires individually to see where they go to - I would imagine one or two would go to the starter motor and ignition switch / coil, etc

Let us know how you get on with it all

I will do an update if I find anything

Hi everyone and Happy New Year.

After did some further investigation I have managed to find some further information regarding the alarm.

Turns out that the Hella Alarm was sold as an aftermarket product in a lot of motor accessory shops as well as being offered and fitted by some BMW dealerships.

By chance I found someone selling one on Ebay Australia and I contacted them twice!! to ask if they would be willing to sell me a copy of the wiring diagram which I was happy to pay them for but sadly they never responded.

I have attached a couple of photos so you can see what the item looked like.

In the meantime I have been tracing the wires to see where they go and this is what I have got so far.

Hn 1 x Brown wire to horn

Hn 1 x Brown wire to horn

3 x pairs of Brown with Yellow Stripe could be lights and doors, bonnet and boot locks T+ and T - .

2 x Brown wires to MK (Master Key)?

1 x Brown with White Stripe S?

1 x Solid Red wire (30 or 31) goes into a loom maybe onto starter or battery but nothing direct to battery lead that I can see. Also nothing going to coil.

Also checked an on/off switch located in the glovebox which I thought maybe the alarm arming operation turned out to be just for the light and a spare feed.

I need to do more tracing and check around the ignition switch just in case there is something there

The main reason for me doing this is because i read somewhere that these alarms can allow the car to start and then cut out the engine to prevent them from being stolen?

Whether this is true or not I have no idea I just want my car to run again without cutting out!!

Morning Paul

Have you tried contacting Hella Direct they may have a customer services that can help. A friend in Belgium had had a 7 series at around that time he had a hidden Isolation switch that after start had to be pushed or it would cut out. His was under the dash near the centre console. If my old memory is working it cut the fuel pump

Good Luck

Dave

Hi Dave,

Sorry for my very late reply and thanks for the really great idea!!! I hadn't thought about contacting Hella directly as I thought they no longer were in business I will give them a try once I have located their site etc

I remember a 7 series I had for a little while that had a similar thing and a reset switch hidden under the glovebox!!

Hi Dave,

following your advice I have written to Hella and just waiting to hear back from them.

Just a quick unrelated question as I am trying to remember myself!! When you remove the fuel cap from the fuel tank eg when you are filling the car up do you feel or hear a release of pressure?

Hi Paul

Ooo Eerr I will have to check that 😅 I know I do with the wife's Subaru Outback

Just checked the X5 Yes

Dave

Thanks Dave I thought that was the case just noticed the seal around the petrol cap is dry and I couldn't hear or feel the usual release of pressure

Well I finally heard back from Hella and they sent me 2 diagrams (photos added). The reason they took so long is because they were trying to find a set of installation/fitting instructions but sadly they don't have any on record any longer

Here are the diagrams but you may need to learn a bit of German lol !!!

Morning Paul

Translation isn't much of an issue the real question is did it help 🤣

Dave

13 hours ago, Greydog said:

Morning Paul

Translation isn't much of an issue the real question is did it help 🤣

Dave

Hi Dave not sure yet as I have not been ale to get back onto the car of late (life etc has been manic recently) but hope to get back on it later this week

Here’s my input!

I’ll have a better look when I get chance

Ok… so the only thing that stops the signal to the ignition is if the internal relay is activated by either the doors or the bonnet/ boot becoming active.

Once the car has started then I guess the relay is activating and cutting the ignition feed?

On 3/17/2026 at 10:47 AM, X5smw said:

Ok… so the only thing that stops the signal to the ignition is if the internal relay is activated by either the doors or the bonnet/ boot becoming active.

Once the car has started then I guess the relay is activating and cutting the ignition feed?

Yes that is exactly what is happening I think!!! and the only thing I have open is the bonnet as attempt to start the car.

It starts ok then cuts out but because I have had the battery off for charging for example and after I reconnected everything I thought that there was an alarm reset switch in the car which I have been able to trace as yet.

Taking on board what you are saying I will have a look for a bonnet switch too.

It does seem strange that you cannot run the car up without having the bonnet open up if you need to check things over?

Thank you for your help and advice

It maybe that the relay is at fault and does work with the bonnet open normally. … I’ll dm you a way to check.