Factory horn wires

So I’m in the process of wiring my train horns to my factory horns. I know, there’s ton of talks of this subject. The issue I’ve ran into is that I open up the wire loom on the factory horn harness and both wires are blue! I don’t have a multimeter but is there some way to identify which is positive and negative?

 

Try looking here

 

Update… everything is working properly. Ran a toggle switch in the console to toggle between factory and air horns. Got a relay wired up because I was told I needed one ‍♂️. Still waiting on my fuse tap to come in the mail so that I can tap into the ignition fuse for vehicle on power only to the compressor.

 

Looks loud!

Gotta love the wavvvvy tundra leaf springs!

 

Lmao that’s one thing I noticed about these trucks when I was looking to buy

 

I just installed a separate switch for my compressor.