Car horn is going off whilst driving how can I turn off manually?

If it has a separate fuse (consult your owner’s manual), then just removing the fuse is simple and effective.

Otherwise, you can find where the horn is physically located under the hood and disconnect the power wire (or ground, if it has a separate ground wire).

Either of these actions will break the wiring circuit to the horn, which makes it inoperable.

But I’d want to know why it’s doing this action. If it’s just a faulty switch in the steering wheel, then disabling the horn will stop the noise, but it might not stop whatever circuitry is malfunctioning – or the cause of the malfunction – and with so many of the vehicle’s critical controls passing through the steering column, this could mean pending failure of any number of other more critical functions.

Otherwise, if it’s a case of, say, rodent activity on the power wire to the horn which has stripped some insulation so that it sporadically makes contact with a power source (maybe even another bare wire), then it could mean that other wires have also been bared, which can spell unpredictable failure in other systems.

You don’t want unpredictable failures while driving. Find out what’s going on, or have a good mechanic do it for you.

Additional Info: I drove in top of one of those yellow tiles ma
king a left. That’s when it went off

What kind of car? For most of them you can pull the electrical connector off the horn.
Remember to hook it up before you get your car inspected if necessary in your locale.