Need help with wiring

[Mighty]

I understand.  That's what I've found in my research, so far.
 
Everything I've opened up and looked at is screw-on terminals.  I haven't seen any sign of anti-oxidant.  The wires look like bare metal to the naked eye.
 
I know that aluminum oxide is pretty much the same color as aluminum, and that just a glance at it is not a real inspection.  There could be corrosion on there that I can't see.
 
I just looked at one of the original switches, and it is marked CO/ALR.  I just looked closely at the wires in that switch I have open, and I don't see anything that looks like it could be remnants of a paste or gel.
 
My father bought this house when it was new.  He's an electrical engineer, and was fairly hands-on in maintaining the house.  And, was definitely concerned about safety.  I am reasonably sure that if he saw any signs of poor workmanship that he would have had it taken care of.
 
But, as we've discussed, the standards and codes have changed since he was living here.

 

[Mighty]

I'm finally ready to try my Z-Wave switch, (here's the manual) and it's not working.  Here's a picture.
 
In addition to the switch, I got new twist caps, anti-oxidant, copper wiring, and AlumiConn connectors.  In this one fixture, I've installed copper pigtails, and all new gooey twist caps, throughout.  I also went over the end of each aluminum wire with emery paper to remove any possible corrosion before connecting it to the pigtail.  Though, they looked clean, to me.
 
I have tested the continuity in multiple places, marked with dots in the picture.
 
From the Neutral screw on the switch to the twist cap (tests that one pigtail).  From Neutral screw on the switch to a socket in the fixture.  Actually, a socket on each side of the mirror.  That tests all the twist caps and pigtails.
 
From the Load screw on the switch to a socket on each side of the mirror.
 
From the Line screw on the switch to the wires under that twist cap.
 
I actually ordered two switches, and I swapped them out.  Neither works.  I've tried flipping the manual off switch both ways, and still doesn't work.
 
My multi-meter can show voltage.  From the Line screw to the Neutral screw it sees a few mV.  From the Load screw to the Neutral it sees 124v.  That doesn't look right, to me.  It should be the Line that shows 120v, correct?
 
I've double- and triple-checked.  The wire I've connected to the Load on the switch is the one that we identified earlier as the Load wire.  I have checked the continuity from the load screw to the sockets on the fixture.  The wire I've connected to the Line goes to the twist cap, which brings together the hot line with the wires that continue on to the rest of the circuit.  Other lights on this circuit still work.
 
I did one wire at a time when changing over from the micro switch, which worked, to the wall switch, so there would be no confusion.
 
Is there anything obvious that I've missed?
 
I guess I could wire the micro switch back in, and see if that works.  I think I'll send this and then try that.

 

[RAL]

Yes, you should see 120V between the line and neutral, not the load and neutral (unless the switch is On).  If you moved the wires one by one, I'm not sure how you could have got it wrong.  Unless we were wrong in analyzing the original wiring.
 
I would try swapping the line and load wires to the switch and see if that makes a difference.
 
You have a lot of stuff to fit back into the electrical box with the switch, plus the purple wire nuts and AlumiConn connectors.  If you can make it all fit, that's fine (and a bit of a miracle).  My choice would have been to use 3-port AlumiConn connectors and eliminate the wire nuts where possible and also reduce the number of connections.

 

[Mighty]

Yeah, I bought a bag 'o 3-port AlumiConn connectors.  But, I forgot I had them until I was done.  Partly because, in my programming career I've learned to Make It Right Before You Make It Better.  I was trying to be very simple.  If I had a twist cap, replaced it with a twist cap.  If I had an aluminum wire going to my switch, put an AlumiConn on it.  Also, I don't have anywhere where two aluminum wires come together.  It's all either one or three.
 
I would just swap my Load and Line, as you suggest.  Except I just now checked, again, and I definitely have continuity between my Load screw and a socket on my fixture.  That one is just a simple, single wire with a pigtail, so I'm reasonably sure that I'm not confused by it.
 
I didn't get a chance to put the micro switch back in there, yet.  It'll only take a coupla mins to do that, so I'm going to give that a try.  Assuming that doesn't work, which it shouldn't, then I'll pull everything apart and start from scratch.
 
While I was putting all that together I was thinking to myself, "This is going to be a tight fit in the box, but I think I can do it."  Then I remembered that I'm changing from the micro to a full-sized switch.  I already have an extender, which might buy me just enough extra space behind the switch to stash a few of those bits.

 

[Mighty]

Turns out I had a loose connection in there.  I did manage to find a spot where I could remove a twist cap and use a 3-port connector. I haven't tried getting all that to fit in the box, yet.  It's going to be tight.
 
I appreciate you guys letting me bounce ideas off of you.  And, the pointers to proper aluminum connections.
 
I know that I should upgrade the entire electrical system.  And, I will start setting aside funds for that.  OTOH, about eight years ago, a house down the street from me suffered a massive fire.  People in the crowd who knew the family said that they had just had place entirely re-wired, and the contractor had just finished three days earlier.  Makes it a little less than an automatic call.