Hi Simon,
I have checked every wire and replaced some wiring, along with new horns and I have tried another set of horn buttons. I did consider the coupler but have never heard of one failing and cannot find any posts detailing failures. So I assumed the relay as there was nothing else I could see in the wiring diagram that may cause the scenario I'm experiencing. Replace the horn fuse (cabin fuse box) and horn sounds either immediately or within 3mns. Sometimes a constant sound and other times a short burst or two then constant. I am No expert in electronics but surely a short circuit would not display that random behaviour but my albeit minimal knowledge of relays tells me it could be relay failure. Does rave detail how to remove the horn relay without a tow rope or a slide hammer
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Thanks. Lee.