Horn failure after COM 2000 repair

[DaveyRapier]

Hi long term owner but rarely post. On my 4th 406 now ‘02 hdi estate with 170k, going like a clock

Indicator stalk was in a poor state the slightest touch had me indicating left and right, so got a new plastic spud and spring from eBay and fitted now they work perfectly.

Although now my horn has stopped working since taking the com 2000 unit off, upon inspection I find I am not getting 12v to the horn push on back of the airbag. I am not getting 12v at the plug that comes from inside the com 2000 unit so I fear I may have broken the ribbon cable when I was removing or working at the unit.

So I now plan to wire the horn to a push button or switch as I do not want to replace the whole unit and I only need the horn to pass mot as I never really use it. I have found some diagrams on google which show the feed is from fuse 5 in engine bay (have checked it btw and it’s fine) I need to find the relay for the horn it may be relay4?? But can anyone tell me where it’s located? Engine bay or under steering wheel? Pics of actual location or diagram would be great. Hope this makes sense, thanks!

[steve_earwig]

I'm afraid it's relay 4 in the engine fuse panel, it's mux controlled from the BSI. I can tell you which connector the feeds exit on (cable 10PR-16-way green pins 7 & 15) and which wires (1500 & 1501), but I don't think you'll be wiring into the relay.

Looking at the guide to refresh my memory, I think it all should exit the com via mux, so I'm not sure if you could loose just the horn.

[DaveyRapier]

So are you saying it can’t be done? Will I need to replace the com unit then? This mux is a bit above my head.

[GingerMagic]

Is it possible to wire directly to the battery, with an inline fuse?
If you are only using a push button horn it can be mounted anywhere you like..

[steve_earwig]

Just a matter of running wires through the bulkhead...

So are you saying it can’t be done? Will I need to replace the com unit then? This mux is a bit above my head.

Anything can be done, it's just a matter of difficulty and expense. I can't remember how the horn is run on the com, It's too long ago that I changed mine and I've recently binned the old one sadly. It must be mux though, it's on channel D on the engine fuse panel. You can get to the fuses though, they're (allegedly) 11 & 12.

Mux is some form of addressing, instead of everything having its own wire it's all on the same system with it's own code. When you press the pad the com unit thinks "aha! The driver wants to use the horns", this then tells the BSI of this fact, the BSI then sends a message to the engine fuse panel, along with everything else it's doing, with the address that means the horns, the relay closes in the fuse panel and the horns go beep. Think of it like a letter going into a postbox... Hmm, maybe not

[GingerMagic]

There are 2 holes in the bulkhead, one each side about halfway up the footwell, about 12" from the centre part of dash....

[PeterN]

You should be able to pick up a 12v supply from the internal fusebox.. Check for one that comes on with the ignition - at least 10 amps, take the fuse out, solder a wire onto the blade and re insert it so that the wire is on the fused end.

Peter

[DaveyRapier]

Anybody got a list of fuse numbers for D9 HDI just to make sure I’m not missing something stupid?

[steve_earwig]

Iffy diagrams here (now they are anyway)




These seem to be fairly accurate for most full-mux cars but I can already see it only lists one fuse for the horns, while Serdre says 2 (15 & 7) I'm afraid I've no idea which is correct (and no way of finding out either)


There are some more here http://www.peugeotlogic.com/#fuses (list in the box to the left)

[Doggy]

Steve, the Imgur link took me to my own content - I'm pretty clueless with this stuff but couldn't stumble on the diagrams....

Strewth mate that peugeotlogic link is a real beaut, not seen that before.

[steve_earwig]

Dammit Thanks for telling me. I already posted them on Photobucket yonks ago but now they're putting a watermark all over everything. Simples, I thought, post them to Imgrrrrrr

And the album is... empty. What the f...?

Uploaded again, post fixed. I thought I'd better link the pictures here, not the album...

[steve_earwig]

Btw is it my dodgy eyes or does that say "Horm"?

[DaveyRapier]

Ok just to update this, managed to get my hands on a replacement com2000 unit (2nd hand) from a local mechanic, fitted and all worked fine. Horn beeping perfectly.
5 mins later took the car to the shops and tried to push the horn for another test while driving and it had stopped working again hateful!
Managed to investigate a bit today, I am now only getting 4.8v at the back of the airbag (don’t know what I had when it worked as didn’t check) I assume this is not enough to energise the relay for the horns?? Any ideas as to why this would be as I’m getting a bit fed up with it now? Damaged cables? Don’t think the ribbon had got damaged as I counted turns to centre it before fitting to make sure and also the airbag light is not on so I don’t believe they have got damaged.
Voltage drop somewhere, maybe a bad plug connection? Anyone know which plug is for the horn? There’s 4 on the back connection to com2000 unit

[DaveyRapier]

Also this is my fuse box in engine bay, no relays in here. Not the type I’m expecting to see anyway. I’m looking for small square shaped items with pins on the bottom? What are these plugs for in between fuses?

[steve_earwig]

Plugs are for wiring? Not sure what you mean. The 15 amp fuse towards the bottom r/h is probably (if the diagram is correct) for the horm. Apparently 5 volts is correct for signalling on car electronics. Were you getting more than that before? I'm fairly sure there is no individual wire for the horm leaving the com - it's mulitiplex. Relays are tiny things on the circuit board inside.

Not really sure what to suggest from here. The horn contacts on my D9 were quite grotty, one of the things I did in there was give them all a file as it only worked sporadically before, would it be worth checking them? Clutching at straws here...