Took delivery of the car a few weeks ago and couldn't believe how pathetic the horn was. Ended up ordering a twin Hella kit with splitter wire included and looked for some guidance on best way to replace the roadrunner sound installed. Mostly worked it out myself but thought I could help others. Firstly, it's located behind the bumper on the nearside (UK model) and the easiest way is to remove the fog light. Use a trim removal tool and gently prise the trim around the light out from the bumper, starting nearest to the centre of the car. Prise the rest of it out working towards the wheel, be careful with the last part as the clips on this bit pull towards the front of the car. Then remove the 3 torx bolts (T25) from the fog light and pull the light out, remove the wire connection and place it out of the way. The original horn is clearly visible in the gap. This can be removed with a 13mm socket and the wire disconnected. Clip the splitter wire into the original harness, plug in the new horns and test to make sure they work! Bolt the bracket to each new horn and mount with the original 13mm bolt through both of the new brackets. Make sure they are positioned out of the way so that your fog light has room to go back in and cable tie the new wires out of the way so they can't jiggle about. Replace the light by plugging it back in and tightening the 3 screws to hold it in place. Push the trim back into place and test that fog light and horns still work.

Hope this helps, took me around half an hour.

The Fabia Mk4's single horn's performance was previously criticised here last year

https://www.briskoda.net/forums/topic/530845-feeble-horn/#comment-5926126

The standard horn's sound quality and output don't concern me enough to bother swapping it for something more tuneful/savage, but it's useful (for me) to learn exactly what's involved in removing a foglight just in case a bulb-replacement should ever be needed.

They were definitely right, but I felt it was that weak, it let the car down!

I did this many years ago when my wife got her first MK3 I think, Fiesta, then I transferred it to her next Fiesta.

Our older daughter bought a new SEAT Ibiza 1.4 SC in 2009 - and it had only one horn, sounded very "nasty", probably stopped me using the horn when I looked after that car for a couple or so years later on.

@Prillerthriller

May I ask from where you obtained the kit comprising the two Hella horns and that included the supplementary 'splitter' wiring harness?

I notice that there's a current advert on AliExpress for the two Hella horns and splitter harness for £11.59 + £7.39 delivery. For around £20 and (reasonably) straightforward installation, it would almost be a no-brainer.

Edited 20 October20 Oct by DerekU

That's exactly where I got it, and yes, it's very easy to fit. BIG improvement.

Thanks - I tried to provide a link to the £11.59 AliExpress advert I found, but, as its URL-length is very long, I used my usual URL-shortening app to cut its length down. I checked, after posting my comment, that the shortened version was OK, but it did not work, so I edited it out.

Hopefully, using a different URL-shortening app, this link does work.

https://shorturl.at/TE9KS

(And it seems to...)

Edited 20 October20 Oct by DerekU

Yes, that looks the same as the one I got, much better sound.

I eventually decided to replace my Fabia Mk4’s ‘peepy’ single horn with the Hella twin-horn set-up described in detail by @Prillerthriller above. I won’t be doing this until the weather gets a lot warmer, but some comments now on sourcing the necessary parts may be of interest.

@Prillerthriller managed to obtain the Hella twin-horn kit and add-on ‘splitter’ wiring harness as a single order from Aliexpress, but I was unable to do this. I bought the add-on wiring harness alone from Aliexpress for £17.24 (£9.79 + £7.45 delivery-charge) but sourced the Hella horns though ebay (£16.51 including delivery charges and with a discount voucher).

To allow immediate connection of the Hella horns to the add-on wiring harness, care is needed when sourcing the horns. The appropriate Hella Part Number is 3FH 012 010-021 that gets you a box marked TE26 SET TRUMPET HORN QUICK FIT. The box just contains the two horns (one 500Hz, the other 400Hz) and an instruction leaflet - but no wiring harness. I suppose this makes sense as the length of each 'branch' of the Aliexpress add-on wiring harness is about 500mm - which will be plenty long enough for a Fabia Mk4, but may be too short for other VAG models.