I’m planning on purchasing a P3 VERY soon and I need to know… Is it a really bad idea to get one of these horns if you can’t install a manual valve? I really don’t see anyway I’ll be able to stretch a line into my Dodge Dakota cab without doing some serious work to get it in there…
not a bad idea at all, just not as fun to blow IMO. You think it would be to much work to put in a manual valve? Something as simple as this, 
Well… I also like having a foot pedal electronic switch. It becomes a natural reaction when you hit the breaks for some idiot ;).
Just get a electric valve solenoid and a momentary switch for in your cab. It will not hurn the horns and it is WAY easier. I had a manual ball valve when I first got my Leslie and it was a pain. A lot of wasted air and hard to control. A Graham White Valve is another idea. If you do want a manual valve, this is the way to go. Very easy to control the amount of air that goes into the horns. You will have to route hoses into your cab though. And plan on spending around $100 for just the valve.
Sounds good! I’ll just buy another foot pedal switch :D.