Here is where I ended up placing my switches. Turned out nice!
Now, i’m sure I will need more wire than is supplied with the kit to run my switches to horns and etc. What type of wiring should I get, gauge wise? 12? Speaker?
And also, I haven’t gotten a PSI Gauge yet (plan on getting the digital air zenth). Once I turn my compressor on, how will I know when to turn it off? Or will It do it automatically because of the pressure switch?
Your pressure switch will turn it off, as will your switch on the dash if you’ve wired it correctly.
This is how I have mine setup, and when I had a line blow out that switch came in handy.
-Kris
The 540 kit comes with 20ft of 18ga wire. It is meant for your trigger wire to the pressure switch.
12ga would probably be overkill for the horn wires. You can go as small as the stock horn wire.
Thanks for the info! I was worried that I wouldnt know when to turn the switch off.
Thats what I figured. seems I will probably have enough for the pressure switch to toggle. But Not enough for the horns switch.
I have a 2013 GMC Sierra Btw
Welcome from nor cal
Seems like I remember reading that the newer Silverado & Sierra horns are negative switched. I haven’t wired my '09 yet to tell you exactly how to go at it…
What does that mean?
Got my horns today and they look awesome!
Traditionally, horns are wired so that they are already earthed against the negative of the battery. When the horn button switch is pressed, it provides positive power to that line (and through the horn). That type of system is positive switched. A negative switched circuit is where there is a constant connection to the positive and the switch, when pressed, grounds the circuit.
You can check which version you have by using a multimeter. Put one test lead against the horn and the other to ground (earth). If you have 12V indicating on the meter, you have a negative switched circuit. If you have no power indicating (and you get continuity between horn line and ground) then you you have a positive switched circuit. Another good pointer is to look at how the stock horn is wired. If there is only one wire (i.e. single connector pin on the horn) then you have a positive switched system because the power comes down the line and the horn itself is already earthed against the chassis through it’s mount.
Essentially it makes little to no difference, but you do have to observe the hookup to your solenoid wire once it’s spliced into the horn wire (either connecting it to 12V positive for a negative switched system; or to ground for a positive switched system)
Hope that’s all clear as mud 
Basically. Check with a multi meter to see if it reads 12v or 0. I believe it is a negative switched circuit because I believe I saw two wires in their last time. So then should I still go off the wiring on the first page??
And I believ I have two factory horns on my truck. I only cut into one harness correct?
Yeah go with the original idea. When you wire up the solenoid and hear it open up as you connect to ground you’ll know you’ve tapped into a positive wire, in which case you’ll have to swap to the negative one. Yes you only need to tap into one horn wire.
Swap as in, cut into factory horn wire negative. And reconnect the positive wire
Looks Pretty confusing… 
Got my tank and compressor mounted. Got my Horns mounted…But my 1/2" line is too short. Can I just order more and use a connector between the two? Or will I need to use only one line from the tank to valve? Can I pick one up local instead of having to order one and wait?
Ideally the line will be the better option but don’t shy away from using a connector. Just keep in mind that the more connectors you run, the more chance there is of having a leak somewhere.
Thanks. I don’t really feel like running the hose again so I’ll use a connector. What hose should I buy? I was thinking of going to home depot and see if they have something that will work. If not I will buy it from hornblasters.
I couldn’t figure out the SPDT switches so I just ran it as a toggle.
DOT air brake tubing with instant tube fittings is great for flexibility and repair.
If I remeber correctly a SPDT switch has 3 tabs with the center tab being common. If the switch has 2 positions then common will be connected to one side or the other. If it has 3 postions then the center postion is off and the common tab isn’t connected to either side.
Thats correct, but my truck has a negative horn wiring.
Only found one leak so far and it was fixed. There is another small one somewhere…hummm
Got my horns working today and they sound awesome. Only issue is that now I have hyper flash with my left blinker? It doesn’t do it to the right, or for emergency lights. Just the left blinker. I check the grounds and they were solid on the solenoid and compressor. I took off the power source to the horn switch and still did it. I don’t have LEDs and it didn’t do this before when I had just the compressor running. Now it does it since I ran the tubing for my horns?
How did you install your solenoid (i.e. where did you tap into your car electrics with the trigger wire for the compressor)?
Couple of things to try first:
The rapid flashing is caused by a circuit that’s designed to measure resistance. If there is no or low resistance then the circuit goes into the rapid flash state with the intent of telling you that you have a blown bulb. I don’t want to cause undue alarm, but problem is that those IC circuits in modern cars are very prone to voltage spikes. If you wired a solenoid coil into an unprotected wiring loom without using a diode, then there’s a real possibility you’ve blown something up.
Check the above points to see if you can get things resolved, but if not… I’d seek the services of an auto electrician to diagnose it.
I’m an idiot. One of my blinker lights is out.