I found a couple posts about the PVC in the tail, and some comments about the change to a spring at the positive contact in the head.. bolding of some words added by me, but no words were changed. the photos that work are from my own image host, links to original threads included in case anybody wants to update the original images
Let's start with the basics. These lights have one positive and TWO (2) negatives. The tube, whatever tube, acts as a ground. When you screw the light together and the light goes on for 1 second then turns off, this is showing that the ground through the TUBE is making contact. The second ground (the spring) activates the light. If you screw the light together and there is no dim light that shuts off, the problem is in the contacts with the tail or head and the tube itself. If the light turns on dim then shuts off but the switch does not work, it is more than likely an issue with the spring not making contact.
Let's look at two tail switches:
The switch on the left is lacking the super-heavily engineered, long talked about... plumbing part. The first thing to do is rip this sucker out. It is only in there to keep pressure on the battery during HEAVY recoil of a weapon. Do you have this mounted to your .44 magnum or .308 rifle? No? Get rid of it. 90% of the time when there is a problem, it is not letting the spring make contact with the tail. That large, flat silver part inside the retaining ring is what the spring needs to make contact with. Make sure it is clean.
Now, lets look at the conection between the head/tube/tail.
As you can see, the tube on the left is rounded and the tube on the right is cut out to fit nicely over the retaining ring both the head and the tail. The left tube is a 17670 tube and the tube on the right is a standard 123 tube. All that matters is that the tube makes contact with the retaining ring (in a Novatac) or the outer ring in an HDS. When using these tubes, or any other tube on a Novatac, you want to make sure the spring protrudes evenly. If the spring makes contact with the retaining ring, you can have the light change settings as though you pushed the switch. It can sometimes do this if you hit the light on the side, thereby moving the spring to make contact with the retaining ring.
As the picture below shows, you must have the spring protruding from each end of the tube.
If the spring does not protrude from each end... stretch that sucker so it does.
Also, be sure that the retaining ring is nice and tight in both the head and tail of your Novatac. Loose retaining rings cause congestive heart failure, high blood pressure, and strokes, usually preceded by lots of cursing.
Sometimes the spring can fit around the HELTAPP (highly engineered, long talked about plumbing part). It helps to put the tail on first, making sure the spring goes over HELTAPP.
Again, make sure that there is spring protruding from the top of the tube as well.
Sorry, was :buddies: when I took that picture. Looks clear to me! If you squint and jump up and down, it almost looks very clear.
Now screw the head on and...
Let there be light. Well, first a second of dim light followed by bright light when you push the switch.
First big change I see if the addition of a positive contact spring instead of the brass nipple.
From the serial number, this is the third run of Novatac lights, so vendors may have, and most likely did, change. I doubt that the soldering was done by a different vendor, but it is possible. I would need to look at the light first hand to say any more than this.
The addition of a positive contact spring was something that was always desired as it helps keep the battery terminal from losing the connection during recoil.
I've been waiting to see how the third gen would turn out. Glad I have first and second.
I must say though, that when NT first came out, there was quite a stir on the forum regarding things that people thought were there to cut costs, but in actuality, increased costs. One example is the polycarb lens. Optical grad polycarb was used and cost a heck of a lot more than UCL. It was done so the lens would not break... ever. Even when thrown as hard as one could at a cement wall. (Did that!)
This though... this does look like other vendors were used. Perhaps to cut cost, or perhaps because the previous vendors could no longer supply what was needed (this happened more than once).