Help tracking down air leak

NAPA had them. I had to convince the guy to look though...

 

Yup...2 more..


Ok..fixed that. No more leak there...

WAIT WHATS THIS?? - new leak..new hiss?! - OK, so maybe while this 1st thing was bad, it wasnt the entire story.

Next up? - the alum manifold to the LEFT of this one. It has a ton of GREEN (Secondary) hoses going to it. On the bottom is what looks like a pressure unit with a few wires going to it. It is leaking at the manifold. Got a wrench in there and finally got it out. Cleaned the threads and will re-install and see if I can tighten it up. It was a bit loose as it was. Didnt take much effort to remove.



..Anyone wanna buy a rig CHEAP!?

 

OOPS.

Well, I put the thingy back in...and the threads no longer leak bubbles.
In fact, I have sprayed the #### out of all of the fittings and threads and hoses I can find and I still hear this leak.

My best guess is this electric pressure unit on the GREEN block at the lower right.
I cant tell for sure. I have soaped up ALL of these 'wired' things and ran my fingers around them and NO bubbles but I hear air escaping from something... I took a piece of tubing (to act like a stethoscope) and it APPEARS that the sound gets louder when I go near this ELECTRIC thing on the green block:



Whatever it is..IS intermittent. Most of the time when you press in the tractor parking brake valve - you hear this HISS but sometimes (2 out of 8 times) you dont. I think if I had a leaking hose at this point, it would ALWAYS leak and keep leaking.

What do I do next?

 

So the thing with the 2 white wires and 1 green wire is the brake light switch?

I suspect that is the cause, but not sure and getting tired of not finding this. At least the fittings I changed WERE leaking but that was not the main cause of any of this HISS...



How does this switch work? - I had thought the manifold was always pressurized. If not, that might start to explain things perhaps.