Switch Disassembly, Repair, and 1980 5D Restoration

This is part of a series of posts I've written about common Maglite repairs. I've also covered the following topics:

Removing Battery Corrosion and Straightening Bent Lights
Stuck Batteries
Stuck End Caps
Stuck Retaining Rings
Switch Removal and Stuck Switches

Disclaimer: I'll start out by saying that these repairs are tedious and challenging. It is very rewarding to make an old Maglite light again though. If you have a special light and don't feel up to the challenge I do restorations and custom work on most vintage flashlights. My contact info is at the right side of the page.

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When a Maglite fails to light some of the problems are fairly obvious. Dead batteries and bulbs are fairly obvious solutions and those are easily diagnosed by changing the battery or bulb. Maglite even has it's own factory service manual which can be found here. But what should you do whenever everything appears normal but the light will still not light?

This is a fairly common problem I've encountered on restorations and I've run into it on a 5D light I'm restoring for someone currently. As you can see there is no visible corrosion or damage but still it won't light.

The common sources of this problem are internal corrosion of the switch or corrosion of the tail spring. If you have an extra working switch and tail spring they can be easily swapped to diagnosed the problem and most users opt to purchase a new switch at a cost of around $12 rather than try to diagnose the non-working switch. This is an easy, inexpensive fix but I'll still go into how the switch mechanism works and how it looks as well as some simple fixes. I prefer to leave the light as stock as can be and always try to fix parts over replacing them.

To understand how the switch works we must first understand how the light works. In order for the light to work current must flow from the negative side of the battery to the positive side.

1 - The positive side of the battery sits up against the switch and the current flows up to the plunger.
2 - The plunger opens and closes the circuit.
3 - On the opposite side of the plunger the circuit picks up again. This connects to the positive terminal of the bulb. If you look closely you can see that this terminal is wrapped in a plastic insulator. This insulates it from the housing of the bulb which acts as the negative terminal.
4 - The housing of the bulb then connects to the negative contacts that slides along it when focusing.
5 - This is connected to the body of the light through the set screw.
6 - The body of the light is connected to the tail spring and back to the negative side of the battery and the circuit is complete.

You'll notice that this switch is specifically for a non-letter serial light. However, all flashlights work in the same manner. Most aluminum and steel lights flow current through the body. The voltage of the batteries is relatively low so you won't feel a shock as the current is drawn back to the negative terminal of the battery rather than to ground. Because the batteries generally have a low voltage any internal corrosion of the switch or tail spring will usually generate enough resistance to stop the flow of current. That is the case with this 5D I'm working on.

So let's take a look at a working Maglite to see what kind of resistance we're talking about. Shown below is an multi meter set to ohms (a measure of resistance) hooked to the positive and negative side of a new switch. As you can see it reads about 11 ohms. It should be noted that the switch must have a good bulb in it and the switch must be in the on position otherwise the ohms will not register.

The body and tail spring will provide negligible resistance. Checking the resistance between the edge of the end cap that is not anodized that sits up against the very end of the barrel and the end of tail spring confirm this as shown below. Typical resistance is around 1 to 5 ohms depending on the amount of corrosion on the spring.

Now we have a good baseline. We know that ideally the circuit operates with a nominal resistance of 11 ohms. So let's take a look at the light I'm working on and see what kind of resistance it has and I'll see if I can get it's resistance down to the resistance of a good assembly. Shown below is my switch removed from the light and hooked to my multi meter. This removal process can be found here and elsewhere on Youtube.

You can see that the switch has infinite resistance which means there is a part that is not making a connection somewhere or is missing and is inhibiting the flow of current. Next I'll open up the switch and test the individual parts to see if I can find the culprit. This process will be detailed below. All of the values obtained should add to be the total resistance of the switch. If you have a resistance of 60 ohms and you find one part that is 45 ohms you can stop testing because that part is the problem.

As can be seen below the positive battery contact to the positive bulb contact across the plunger has an infinite resistance when engaged. This is most likely the culprit. However, I'll clean all of the electrical contacts as shown below to ensure the circuit operates properly. I'll soak these parts in vinegar and then wire brush them. DO NOT soak steel parts in vinegar because they will corrode. Make sure you only soak the parts shown below as they are copper and aluminum.

Pay extra attention to parts that have visible corrosion as the corrosion is the likely cause of the higher resistance. The set screw and negative bulb housing contact as shown below are a likely culprit as well. This contact rubs the bulb housing and the wear causes it to corrode or the set screw itself corrodes because of the dis-similar metals contacting each. See below for an example from this light with a lot of corrosion.

Shown below are the cleaned up parts. The copper parts should shine like a new penny and you'll notice the resistance is remarkably lower.

Shown below is the resistance test of the switch after I put it all back together. You'll notice it is only 0.8 ohms which is basically the resistance of the bulb. Why the difference vs. the "new" switch above at 11 ohms. Well mainly because the copper parts will naturally oxidize (corrode) over time due to even the most minuscule amounts of moisture in the light which ups their resistance. Right now the light is clean as a whistle but with normal use and exposure to the atmosphere the copper parts won't keep this shine. That's ok though. The corrosion stops after a natural layer has formed and the switch will average out at around 11 ohms.

Maybe you've found the switch has the same resistance as a new switch or that the light still won't work. The next item to check is the end cap and spring. A lot of times if there is a lot of resistance you'll notice that the spring is corroded, the spring seat is corroded, or the non-anodized edge is not making contact with the end of the barrel. All of these items must be completely free of corrosion so that their surfaces all make contact.

With all of the parts now free of corrosion did this light shine again? Judge for yourself in the pic below. So, why did I save this light? Well, another collector I deal with asked me to. Also, it is stamped "Paten Pending" opposite the serial number and lacks the features of a 1979 light so it is a 1980 light. It's from only the second year of Maglite production and is serial number 49,126 so it is relatively low. Please see my Quick Dating Guide if you're interested in these details. The light is nearly 40 years old and in excellent condition other than the non-operable switch so I figured it is a worthwhile restoration especially because someone valued it all these years to keep it going. Here are some pics of the light after it was all repaired.

This light came from a fellow collector who picked it up at an estate sale with the above accessories as well. The estate was from the owner of a large Tennessee construction company and this was likely a personal light of his. A personalized 1980 3D also came with it. The 5D bulb is an old "Safari-Star", a knock off of the Magnum Star Maglite brand produced by police equipment company Safariland. The Maglite belt suspender carriers the old Maglite logo embossed into the leather and on the package so it is from 1980 to 1984. This will certainly make a nice addition to his collection now that it's all back in working order.

As always I'm looking to buy Vari-Beams and Vintage/Rare Mags. Please let me know if you have any, top dollar paid.