A Maglite seems to be a most durable flashlight, but mine suddenly flickered "off" while I was using it. After a couple of attempts to turn it back "on," it went "off" and would not come back "on." The batteries and the bulb checked out as good. I decided the switch had to be the problem.
This Instructable will offer two solutions to fixing a bad switch on a Maglite using 2 "D" cells, other than ordering and installing a new switch from Maglite. These solutions should also work on models using 2 "C" cells, or more than 2 "C" or "D" cells.
Update: Had I registered this flashlight when it was new, and had I remembered Maglite offers a lifetime warranty, and had my search engine turned up the guide to replacing the switch on Maglite's web page, I could have saved myself a lot of trouble. But, I am also the kind of person who is not really happy until he has dismantled things he owns to see how they work and to make an improvement here or there.
Step 1: Determine the Series
The serial number is located on the flashlight's barrel near the front. Mine is a "D" series. There is also a "DL" series. This video for taking your Maglite apart. I was working from instructions on a web site that no longer exists and came to a dead end. I decided I was on my own.
Step 2: The Switch Sub Assembly
This is a graphic I did of the Switch Sub Assembly after it has been removed from inside the flashlight's barrel. See the next steps for its removal. I made a graphic rather than a photo because I was very uncertain about how this project would turn out. I am recreating vital steps with graphics.
You can see the fins I broke off. Although two are shown, there are actually four. The Switch Sub Assembly is made of black plastic. I left most of it in the neutral tones rendered in Google Sketch Up for clarity. It is possible to order the switch or the Switch Sub Assembly at this web site. Be aware you will need a couple of special tools, too. When you are finished, the total cost will be almost as much as a new flashlight. I wanted a solution that is more durable, or that I can replace myself without ordering parts from Maglite.
The bulb socket is spring loaded and can move up and down. Part of the reflector rides on the brass follower. As the head of the flashlight is turned, the angle at which the reflector is cut allows the bulb socket to move so the beam of light can be focused from wide angle to a narrow spot.
You will need to remove the Switch Sub Assembly from the Maglite, but more about that later.
Notice the contact for the battery tip that runs through the bottom of the Switch Sub Assembly. There is a corresponding contact point directly across the opening for the switch, which is below the spring under the bulb socket. The switch bridges between these two electrical contact points.
Step 3: How I Removed the Switch Sub Assembly
According to the web site linked in step 1, you use a special tool to unscrew a retaining ring. Then you pry the rubber switch seal (# 15 in the exploded diagram from the web site in step 1) from the barrel of the flashlight. Next you use a small hex wrench to loosen a set screw deep inside the switch that digs into the inner surface of the barrel. Then you can slide the Switch Sub Assembly out of the lamp end of the flashlight barrel. But, I encountered a big snap ring instead of a threaded retaining ring. At this point I believed there might be a shoulder toward the rear end of the barrel that would keep me from sliding the Switch Sub Assembly out of the rear end, but that proved to be false.
What I did is a bit different. I went to work at removing the large snap ring. First I removed the rear end cap and the batteries. I removed the head of the flashlight with the reflector and lens. It unscrews just like the rear end cap. I removed the flashlight's bulb. I drilled a hole into the plastic Switch Sub Assembly between the ends of the snap ring.
Step 4: Move the Snap Ring, Hook It, and Pull It Out
This is the same view as in the previous step, but the snap ring has been pushed in the direction of the red arrow so the other end is now positioned over the hole you drilled. I used a piece of thin enameled copper wire to hook the pointed end of the snap ring. The hole made it possible to get under the point of the snap ring with the wire loop. Then I pulled the snap ring out with a needle nose plier.
The beige steel tube in the photo is from an old patio umbrella. It made a good driver for pushing the Switch Sub Assembly out of the bulb end of the flashlight. I forcefully jabbed the flashlight downward in the direction of the red arrow until I had driven the Switch Sub Assembly out of the flashlight barrel. The process was a lot like setting a steel fencepost. In the process shattered pieces of the old switch came out with it. At this point my plans were very indefinite and I did not know if the Switch Sub Assembly would work for me, nor did I know if I wanted to use it again. But, the Switch Sub Assembly emerged undamaged, other than the switch parts. Afterward, I reinstalled the snap ring. By this time my plan was taking shape and I realized I would need the snap ring to keep the Switch Sub Assembly in its proper place.
Step 6: Missing Part of the Circuit?
The photo shows my attempt at a cutaway diagram of the flashlight's circuit. The copper and black rectangles are the batteries. The red lines indicate the current pathway. You can see a black profile of the Switch Sub Assembly with a round void for the switch. The blue lines define the profile of the reflector, and this shade of blue is its actual color. The larger yellow ball is the bulb. The small yellow ball is the brass follower pictured in step 2. The aluminum case is part of the circuit, but the finish coating is a dielectric (insulating) coating. I could not determine how Maglite connects the flashlight case to the side of the bulb socket to complete the circuit. I needed to make a positive pathway of my own for this part of the circuit.
Step 7: Completing the Circuit
While the Switch Sub Assembly was still outside the flashlight barrel I used my electric solder gun to place a little solder on the brass follower. I tinned the end of a piece of stranded wire about 20 gauge with solder and then heated the solder on the follower to make a good solder joint with the wire. I cut the wire at about 1 1/2 to 2 inches in length.
I drilled through the flashlight case between the hole for the switch and the "O" ring seal in a place that would be hidden by the flashlight head when screwed back onto the flashlight. I tapped this hole for a 6-32 brass screw. I started the screw with a needle nose plier. I used an offset screwdriver to tighten it as much as possible. With my soldering gun I added a dab of solder to the 6-32 screw head, but it is not yet time to solder the other end of the wire to the 6-32 screw's head. A replacement for the switch must be handled first. In the meanwhile, it is a good time to cut the excess from the screw on the outside of the barrel and file it smooth.
Step 8: A Very Simple, Effective, Cheap, Durable Switch Replacement
This is option #1. It may not be the option you choose, but it is worthy of consideration. Cut a 1/4" aluminum rod to a length of 3/4 inch. Bevel two sides of each end so the rod will fit between the narrowed areas over the electrical contact points in the opening for the switch. The upper contact point (not visible in the graphic) is spring loaded. While this aluminum rod makes good electrical contact, it needs some physical reinforcement to keep it from falling out of place if the flashlight is ever dropped. Place some hot glue around both ends of the aluminum rod to keep it in place. Later, when the flashlight has been fully assembled, the switch hole can be covered over with hot glue to keep the flashlight waterproof. In order to avoid using massive amounts of hot glue, fill most of the cavity with wadded small pieces of paper, and fill the last 1/4 inch or so with hot glue.
Step 9: Follow Up to Option #1
Option #2 will involve installing a replacement switch somewhat similar to the original switch so the flashlight works as it did originally. But, if you choose option #1, insert the Switch Sub Assembly into the barrel from the rear end of the flashlight. When the wire soldered to the brass follower reaches the 6-32 screwhead, heat the head of the 6-32 screw enough to melt the solder and fuse the tinned end of the wire to it. If you choose option #2, you will solder the end of the wire to the screwhead after the replacement switch has been installed.
Step 10: Option #1 "on" and "off" Switch
The end cap will be the switch with option #1. Twist it about 1/3 of a turn counterclockwise to turn the flashlight "off." Twist it clockwise until tight to turn the flashlight "on." Although the end cap uses metal threads, they are coated with a dielectric and do not conduct electricity. A knurled area on the end cap meshes with the bare aluminum end of the barrel to make electrical contact.
Step 11: Option #2
I chose option #2 for my flashlight. I settled on a switch from Radio Shack (stock # 275-1565). It is small enough that I could install it inside the switch opening in the Switch Sub Assembly and slide the entire package into the rear end of the flashlight.
This switch has a nut and a threaded body. I found a flat washer with an inner hole the same diameter as the threaded body. I had to grind the outside diameter a little to make it fit into the round switch opening. Although my graphics do not show this detail, there is a shoulder inside the switch opening on one side. This made a very good resting place for my switch.
I tinned the two contact points in the switch opening of the Switch Sub Assembly. See step 2 or step 8. I soldered two pieces of stranded 20 gauge wire to the contact points and then soldered the other ends to the switch. The square corners of the red switch button and its black housing were in the way when I first tried to slide the Switch Sub Assembly back into the flashlight, even when fully pressed down. I touched them to an abrasive wheel and rounded them off until the whole assembly would slide into the flashlight barrel. Note: the red switch button pries off of the rest of the switch fairly easily.
Step 12: Option #2 Switch Installed
This photo shows how much I had to cut the corners on the Radio Shack switch down to fit into the flashlight barrel. It also shows the switch in place.
Before you slide the Switch Sub Assembly fully into place, be sure to solder the end of the wire to the 6-32 screw as shown in step 9.
Remove the red switch button and push hot glue into the opening around the switch as much as possible to hold the switch firmly in place and also to make the flashlight water tight. It is recommended that you pry the red button off of the switch first. Then trim away excess hot glue that might restrict the free movement of the switch. I will probably try to make my efforts with hot glue here a bit neater.
Step 13: Works Like New!
My Maglite now works like new again. If it ever fails again, I can remove the Switch Sub Assembly and install a new switch from Radio Shack for about three dollars. I will need to desolder the wire connected to the 6-32 screwhead. I will likely drive the Switch Sub Assembly out the rear end of the flashlight this time so I do not need to bother with removing the snap ring in steps 3 and 4.
I am disappointed that my Maglite failed. I really did not use it that much, even though I have had it for a few years. It feels good that I am independent of the Maglite parts people now.