5 
5 How to get at an end button switch
Some time ago I got a Qbeam 3 C-cell flashlight to keep in our Explorer. It was very rarely used, but the other day I noticed it was on just sitting in its spot in the rear pocket of the driver's seat. It looked like low beam, but the batteries were down only a little. On unscrewing the base I found corrosion just inside the tube and around the base's edge threads, and an apparent thin copper foil boot over the base's spring wasn't green but was in pieces. I cleaned out the corrosion and will treat the corroded areas with DeOxit, but in testing continuity on the base, I find that no matter the switch button position there is continuity between the spring and the base's aluminum threads. With fresh batteries the light will not switch off, and apppears to be stuck on low beam.
Any idea how to disassemble the base to see if it's repairable? There is a plastic plug in the base, surrounding the spring, with two holes in it such as some devices you can unscrew with snap ring pliers, but I can't get that plug to budge. I’ve tried PB Blaster penetrating fluid around the edges of the plug… assuming it does screw into the base, and drilled the two holes deeper to accept plier prongs better, but the plastic plug still won’t turn.
It was an expensive flashlight, seems well built, and was once sold mainly by Home Depot I think, but the manufacturer may not exist anymore. Apparently the inner aluminum threads have swollen enough from corrosion to make the plug immovable?
Esta é uma boa pergunta?
Some ideas to consider. The corrosion may have swelled the fit between the white plastic and aluminum end cap. Whether threaded or pressed on, maybe applying heat from a torch around the perimeter may allow penetrant to seep between plastic and aluminum. If threaded, this may loosen the corrosion bonding the plastic to cap. Drilling into the two holes for needle nose pliers may help as a home made tool, if the cap is threaded. If plastic is pressed on, the forced fit may take some more imagination to remove it. Apply heat only enough to make it too hot to touch but not enough to melt plastic and rubber. Aluminum absorbs heat quickly and gloves needed to handle it. Unfortunately, knockoffs copying Maglite (mine is 40 yes old) are everywhere.
por F Dryer
Heat didn’t loosen it, but softened the plug so the pin holes broke down. I softened it enough to pull the plug out with long nose pliers. It had threads and the aluminum was indeed corroded through its black coated threads. It is obvious the plug was just there to keep the spring centered. Deep in the base, apparently covering the actual push button mechanism and surrounding the spring, appears to be a metal “washer” also having pinholes, but my pinhole pliers can’t get it to budge either. So I’m now letting PB Blaster soak around its edge overnight. It’s so aggravating how aluminum flashlights corrode, even black coated parts some distance from the batteries.
por Hafcanadian
Dissimilar metals in contact with each other creates a galvanic reaction resulting in a chemical loctite. Air exposure on bare aluminum creates oxidation as a hard coating, dull gray. Hopefully, you're able to disassemble the remaining parts to repair the pushbutton. If possible, use some grease on all exposed aluminum not anodized (chemical treatment as a color to prevent corrosion. The exterior is anodized, only a few thousandths deep.
por F Dryer