CIverson – Thanks for the confirmation. Kind of what I had thought.
RedRam401 – I have given train horns some thought also, but I live 5. 5 miles from BNSF tracks and I can hear trains blow as they go through a little town. Not sure I to attract the law since train horns exceed the legal noise level here. My interest is to SCARE, not KILL people that cut me off!!!
stick – Basically the stock installation connects 12V to the compressor and the air valve. The other side of both then connects to a relay, which connects to ground when activated. One side of the relay coil also goes to 12V and then comes from the ECM (somewhere).
What I did was add another relay. I hooked one side of the coil to 12V and the other to my dash switch. Then I disconnected the compressor ground line (which has the pressure switch in series with it) to one relay contact and grounded the other. When you turn the switch on power is provided to the compressor and it runs until the pressure is up and the pressure switch turns it off. The air valve operates normally from the ECM. I have found that even when I leave the switch on all of the time my pressure leaks down and the compressor will run about every three hours. Kind of a kick to hear your truck make noise in a parking lot with no one in it! I have found that the compressor only runs for about five to eight seconds. I got the relay, switch, and necessary crimp terminals and wire from the local parts store.
Thanks everyone. I know what I’m getting for Xmas! Oo.