The NP205 4x4 Indicator switch is an annoying little bugger. They are often broken and are rather expensive to buy. Mine was not working so I decided, meh why not rip it apart and find out whats inside this thing. At first I reached for the hammer to begin smashing it apart... Then I smartened up and brought it over to the lathe and machined the crimp off that is pictured, indicated by the red arrow in the picture below:
The image below shows a normal switch as removed:
The image below shows my switch with the crimp machined off and the detent ball spring fitted inside.
Here is all the parts laid out except the spring, which i left inside the switch as it is a pain in the @$$ to remove.
Here is a picture of the plastic washer used to insulate the spring from the contacts. I made mine out of a piece of plastic from packaging that usually covers the product. You know the insanely hard to remove stuff... Nevermind that black gunk on the body face, i had to tear my nicely rebuilt switch apart to get these pictures.. That's the remains of my old rubber seal.
Here's another of it by itself. I cut it using a paper hole punch, it is the perfect diameter to fit! A little crude but since i took the switch apart to do this post, i will make a newer nicer one.
Here is the spring inside the switch, I made one out of a piece of .045 MIG welding wire by wrapping it around a small bolt. I ground the ends of the spring flat so everything seats square. You have to play with the length a bit. I suggest making it a tad small and stretching it out to fit so there is sufficient spring memory.
I sealed the switch with a piece of rubber cut out of the handle of a roto-tiller. I used a gasket hole punch and cut the inside hole with a piece of sharpened tubing. I then "glued" it on with silicone, careful not to let it ooze into the switch.
When I installed the switch and tested it (set meter for continuity), i noticed it did not work, it stayed on no matter what position i had the transfer case. For some reason the problem was the plastic plunger was not lifting the copper washer off the contacts enough. So i brought the metal body to the lather and machined a tiny amount off the seating surface until the switch work properly. This is a bit tricky. If you machine too much your switch will always be off as the plastic plunger will always be pushing the copper disc off the contacts. I suggest machining 2-5 thou at a time until it works right.
Since the crimp has been machined off, I just siliconed the rubber seal to the metal body and applied a little more around the exterior to seal it and hold it in pplace. Allow it to cure for 24hrs and your good to go.
I found one switch that had failed because the rubber seal cracked and allowed oil to get on the contacts causing a varnish of some sorts. I cleaned off the contacts and it worked fine. Another one had a broken spring. So if it is something simple like that, it won't take long to fix the switch. Like i said before, it took me longer to compile this then repairing the actual switch did.