Little Big Horn

[HPsauce]

Originally Posted by HPsauce

Anyone know the answer to this, or if it's rechargeable off the car?

I think I found the answer by popping open (just taped up) the old horn and freeing the PCB.
The PCB is conveniently labelled +12V, Comms and GND. Though not as I expected.

Taking the pins as 1, 2 and 3 going from the "square" to the "round" end of the connector, they are:
1. GND
2. Comms
3. +12V

Just as well I checked!

[HPsauce]

BUT, looking online I've found a web site selling them (not eBay) that says 1=comms, 2=GND, 3=+12v

Given the style of connectors on the supplied loom, that actually makes more sense.
The unit I bought is a 1K0 951 605C

Does any one know if the positions of the Comms and GND were swapped at some point or vary between vehicles; it seems a bit odd........

Edit: After just a few minutes connected this way to a 12V charger there is more than 6V showing on the pins!
I obviously need to put my meter on the plug in the car and see what that has on it.....

[HPsauce]

Originally Posted by HPsauce

I obviously need to put my meter on the plug in the car and see what that has on it.....

And the answer is +12v on 3 vs 1, without the ignition on.
3 against 2 it's about 9V, so that is consistent with the internal PCB labelling on the old horn.

Looks like I'll need to do a bit of rewiring to use the new horn.

[HPsauce]

And the solution is, buy a 1J0 973 803 plug kit, which is the equivalent to the male connector on the alarms. About £6.

I already have a fly lead with the female 1J0 973 703 connector on, I'm using that lashed up to a 12V charger. I'll fit the new plug on the end, swapping the Comms and GND wires over.
It will then make a good loom extension lead to plug into the (very short) car loom to facilitate fixing the new sounder.

[HPsauce]

Earlier in this thread, as I've just rediscovered, Jim asked:

Originally Posted by The_Laird

can other similar sirens be used as well, such as 1K0 951 605C? It looks the same, comes from the VAG stable and has the same 3 pin fitting, but I don't really understand what the prefix and suffix numbers/letters mean.

He also acquired a rev D which, like my rev C, didn't work at all.

Originally Posted by The_Laird

My 'experimental' approach to fixing the alarm horn (try one from another VAG car) took a step backwards yesterday The alarm from a 2007 Passat arrived in the post (part nummber IK0 951 605D), so I fitted it last night. Same 3-pin connection and, with the little captive bolt swapped for the one off the original horn, it fitted a treat (slightly smaller).

So, set off the alarm and....nothing!

I've done a bit of soldering tonight on my extra loom section and in daylight tomorrow should know whether it is purely a changeover of the Comms and GND connectors or there is something more subtle in the interaction with the control unit between the different versions. Fingers crossed.

[HPsauce]

Originally Posted by HPsauce

whether it is purely a changeover of the Comms and GND connectors or there is something more subtle in the interaction with the control unit between the different versions. Fingers crossed.

The latter I suspect, it didn't work.

I guess that makes sense, if the comms protocols have changed the physical interface has to as well to ensure no-one can mix them up. But as these 3-pin connectors are so common they didn't change the physical shape.

I'll still try again when the "proper" connector arrives just in case it needed some time to fully charge or synchronise or something I've overlooked or connected poorly.

On a positive note when I had the old sounder out I cleaned up all the contacts and made sure they were bent properly to make a good circuit.
And when I took it out of the car today, for the first time ever, it went off as soon as I disconnected it!
Bloody loud too, so I stuffed it inside some shopping bags in the other cars boot - could still hear it for several minutes.

Must have charged up properly overnight, and now its back in the car it's really quite "chirpy", unlike the feeble squawk Adrian may (or may not) have heard when we met up the other day.

Mind you, I've done this several times before.
Bought a part to replace something not working properly. Swapped it, had a good look at the original and fixed it, put it back working perfectly. Kept the new part as a spare or sold it on.

[HPsauce]

A little oddness over recent weeks..................

The horn is now, generally, fairly loud. I have a suspicion that the Maplin batteries I used are fairly temperature sensitive so when it's cold I only get a faint chirp on locking.

But an odd thing is that sometimes, nothing when locking. Silence.
But if I then unlock and relock the car it sounds as it should.

Anyone else observed this or have any explanation? The car always appears to be locked normally and makes all the other central locking sounds.

[Architex_mA8tey]

bad earth on the horn?

[HPsauce]

Could be anything, probably circuit board corrosion/damage lurking from the earlier failed batteries.
So I've finally given up on my repaired old-style alarm horn and bought a new-style one from our sponsors. 8L0951605A from a 2004 A6.

Fitted just now and works fine.

Cleared the low battery errors and they didn't come back (unlike with the old one).
And I'm more confident on monitoring this one and replacing its batteries if/when necessary.

[HPsauce]

Originally Posted by HPsauce

Could be anything, probably circuit board corrosion/damage lurking from the earlier failed batteries.

Odd outcome on this. Today, clearing up, I found the old horn and opened it up.

It was the batteries that had given up and leaked, and they were still fairly new Maplin BN24B's!
The actual circuit board etc. was fine and battery contacts unharmed, but one battery had leakage/corrosion at one end and the other at both ends, plus swelling of the cells (3 flat ones stacked in each unit).