So I was out one day and tooted my horn, It sounded but then sort of dropped slightly in pitch and failed completely. For a brief while all i did was disconnect the spade terminals, reconnect and the horn would work again. But sometimes only once or it was a very short beep.

I figured this was the end of that horn so bought a universal one online. Simple swap but when I plugged in the universal one I get no sound at all. Does the horn need to be grounded using the bracket that holds the horn to the car? or should the 2 cables connecting to the horn suffice in powering the horn?

Fuses are in tact, Relay clicks when the horn is pressed. Spade terminals replaced.

Ive checked with a multimeter. There is a Voltage difference of 12V between the 2 connectors on the horn when the horn is pressed. I checked for continuity with the old horn and there isn't so I can understand why that one doesn't work. The new one does have continuity but also doesn't work when hooked up to a lab DC powersupply (won't let me get to 12V though, as soon as I attach the croc clips the power supply jumps from 12V down to about 5V, the horn also got hot).

Any ideas? Have I just bought another duff horn? Thanks

I'd suspect that the earth side of the horn wiring has failed. Try jumpering that side?

By this do you mean connect a wire directly from the ground/earth spade terminal on the horn to the nearest ground on the car body?

Forgot to mention earlier. I hooked both horns directly to the battery and neither make a sound.

Yep. But if they didn't wotk direct from a battery, then that goes out the window!

The horn has a relay. Not sure where it is on the Mk2, but worth investigating.

When connecting the "new" one directly to the battery it did seem to get a little spark.

I'm going to check the earth side wiring later anyway just to see if there's good continuity and low resistance between car and earth connector.

I know the relay is in the engine fusebox and I can definitely hear it click but don't know if its giving the correct current on output. I think there's another relay of the same type in the fusebox so I'll swap them over to see if there's a difference.

Lastly I know there's an adjuster on the new horn. Going to see if that makes any difference.

Horns are polarity sensitive
One way theyll blown ans horn like ud think it would do

But backwards it either sounds **** or it just clicks so to speak

But if the new horna don't work direct iff battery its doa

Ziggy

So I thought I'd do a continuity check from the earth lead on the horn to the negative battery terminal and grounds to find that each seemed to provide good continuity.

I then set my multimeter to ohms and registered a very low resistance 0.01 on the earth wire.

This made me pretty confident that the wiring was all ok, so I went and bought another new horn.

Plugged in and working!

thanks for the replies!