So I annoyingly failed my NCT (MOT) yesterday as my horn didn't work, so I've done some initial testing today but can't seem to easily locate the source of the problem :-(
1. Fuse box
First test was to continuity test the fuse in the internal fuse box for the horn and check that that was fine - it is (*and I tested all the other fuses just for good measures)
2. Air bag switch
Second test was to disconnect the battery, unbolt the air bag and test the switch on the air bag that it actually closed circuit when pressed - it did. Then I short circuited the pin that this is connected to on the ribbon cable so ground to see if the horn sounded - it didn't
So I guess at this point it's either that a. the horn really is dead, b. the relay for the horn is dead or c. the wiring is broken as I can't seem to think where else the problem might be?
Anyone got any good suggestions on how to locate and test the horn (I believe it is behind the fog lights from searching previous posts) or test the wiring from the steering wheel to the horn? I did try testing from the fuse to ground, but that just gives continuity regardless of whether the air bag switch is pressed or not pressed
Also - I wanted to swap the relay with the fog light relay to see if that was the problem, but can't seem to easily remove the relay to try this as even with the two side 'tabs' loosened it didn't easily wiggle out
Thoughts much appreciated and a few photos attached
Airbag and horn wiring (ground in top left)
IMG_20210903_131821.jpg
Pins for airbag and horn - horn is pin 4, airbag pins 5 and 6
IMG_20210903_131809.jpg
Testing airbag switch to ground
IMG_20210903_132000.jpg
Testing horn wiring to ground
IMG_20210903_132129.jpg
Horn relay - how to remove and test?
IMG_20210903_132235.jpg