After failing my MOT on a few minor points the most worrying thing was the horn had stopped working! I hadn't noticed god knows how loang it hasn't worked.
So i decided to have a look at why it wasn't working myself, first thing to check was the fuse which was fine, now I had to find out how the horn worked.
After some scratching around with a multimeter this is how i think it works :- The horn(s) is fed with 12v all the time and it is switched on the negative side via a relay in the fuse box by the battery.
The relay was checked and was ok, now if i used my multimeter on the amp range I could "close" the switch and make the horn work.
So the horns themselves are fine. So the fault must be between the steering wheel and the fusebox by the battery.
The other side of the circuit works I think like this :- 12v is fed to the steering wheel and when the horn is pressed the 12v goes to the coil on the relay for the horn which closes the relay and switched the negative for the horn,Follow me ?
So I did some searching on this subject on the forum and most horn problems are related the to clock switch (£70+VAT). Bugger that I can fix that myself
, so i took the airbag off the steering wheel (disconnected the battery for 30 mins first) then took the steering wheel off to expose the clock switch(pic below).
Tested this with a multimeter and found all contacts pass through unbroken! so my clock switch is fine! hmmmmm. After looking puzzled for a few mins I decided to look at the circuit board inside the steering wheel (where my radio controls pulg into and the horn contacts) see pic.
The red and black wires on the right are the horn contacts which travel along the circuit board to the connectoron the left for the clock switch.
I tested the continuity between the black wire and the pins on the left side and that was ok, but the red wire doesn't measure AHAH ! a break in the track ? took the circuit board out of its casing (see pic) and followed the track looking for breakes but found none!.
Did some more measurement and found THIS (last pic) not the 20p but the small dot next to it - a 0 ohm resistor had gone open circuit!. Used a bit of wire insted of the resistor.
Relaced everything and hey presto the horn works! yay
wonder how long it would have taken my garage to find that !