2 wiring questions

[Xeek]

1st question:
i havent looked at my truck yet, but theres supposed to be only one wire going to the stock horn, a blue one.
i have a train horn set i want to re-wire into the stock horn with a on off switch incase i want to use only the stock one. wiring page shows: air valve>switch>stock horn. no fuses or anything. i previously had it as: air valve>switch>button>15A>battery.
fine to wire right to the horn wire, no fuse or relay? it would be short honks, max of ~7seconds long.

2nd question:
im adding the 2nd gen overhead console to my truck, i picked up 4 temp sensors for the hell of it(free), i was thinking of having one outside and one inside, how would i wire them with a switch to swap temp sources on the console to them? they each have 2 wires on them

 

[Xeek]

no one?

 

[boominXplorer]

Wire both horns to come on at the same time and just a kill switch fir the train horn. Run a relay switched by the horn power to send power from the battery to your air horn. You can put a switch on the ground wire to to the relay to kill the train horn. You NEED the relay to wire it safely.

For the overhead console using different temp sensors you would need a DP-DT (double pull double throw) switch to make it happen