New to me 4G - electrical questions

[bkaiser]

Has anyone figured how to use the factory air compressor circuit to power a compressor on a truck without air suspension? I think that would be real clean way to add the air horn compressor.

Also a question regarding the 7 pin trailer connector - metering from connector ground to the + trailer feed I cannot get voltage when the truck is off or on. This is true for both the bumper and bed 5er plugs. Is there a fuse that needs to be installed, or a programming option to enable power on this line? Finally, is this constant hot or ignition switched?

Thanks in advance

 

[grabinov]

The factory air compressor circuit is controlled by the computer such that it turns on and off based on the pressure in the factory storage tank and the level sensors at the rear wheels. I think that even if you could locate it, you'd never get all that sorted out. I added a Painless wiring module to my truck to add electrical accessories - stay away from the computer controlled portion of the wiring if you can!

I have had the same problem with measuring the voltage from the trailer connector on my truck, but when plugged into a trailer it charges the trailer batteries just fine. It may sense the trailer connection - through the brake circuit?? The truck definitely knows when a trailer is connected but I am not certain which of the 7 wires it is monitoring to know that. There IS a fancy fuse up in the fuse holder in the engine compartment which controls that circuit. Worth checking at least.

Either way, that charging wire is Ignition Hot Only to ensure that your trailer doesn't run off your truck (or charge off of it) when the truck is parked and still connected.

 

[bkaiser]

Thanks much. I figured the compressor circuit was controlled through a module of some sort, but figured it was worth asking. I have a Painless fuse box on my 3G and it's easy to add. I'll do the same on the 4G.