zulfiqar bhai, i need to confirm this
are both wires of the horn supposed to be at 12v when the horn is not working (with respect to battery negative), if this is the case i understand that the horn works on the basis of potential difference.
on my car, sometimes the p.d between the horn's spade connectors is not the same as battery voltage, rather, 0.3-0.4 volt less.
it is always good at the horn switch (i tested it with voltmeter, it is same as battery voltage.
i think there is a weak connection somewhere, where should i look?