This has been vexing me for months. It's in such an awkward location, wedged between the engine block and the radiator.
The horn crapped out on me last year. As we all know, no horn equals MOT failure. I took it to a friendly mechanic who previously changed my tyres and was quoted 80 quid, because he would have to take off the radiator to get access to replace it. Yeah, 80 quid for a new horn...
So I took it another place, and he used a clever hack of tapping it gently with a long screwdriver and a mallet while I held the button in. It worked! Until a couple of weeks ago.
I asked him if he could repeat the trick but this time it didn't work. He said I would have to loosen the top of the radiator to move it forward, so I could gain access to a small adjuster screw on the horn.
Now, I can do simple stuff like change oil and bleed brakes, but I don't feel at all comfortable messing around with delicate stuff like radiators. The Haynes manual is not at all helpful, only the most basic instructions and one poor quality picture that tells me nothing.
So, I don't feel like I can do the job, but don't want to have to pay that much just to get an MOT. Who would?
Is it better just to buy another horn and attach it to battery, like I did with my alarm system?