One of my replacement .5 ohm heads was giving me trouble, occasional burnt/dry hits as well as random flooding, so I decided to re-wick it and figure out what was going on. I figured out a few potential issues with the heads, but re-wicking them can fix the issue and is easy enough that I went ahead and re-wicked several heads for the practice, and I seem to get even better flavor with the re-wicked heads and even faster wicking action, as I packed the cotton a little looser than the stock heads.
Things you'll notice when rebuilding/wicking:
The coil is a NR-R-NR build, with NR (assuming nickle) tails welded to the coil on either side. After examining several heads, I could see that the weld on some is sloppy and sticks out, potentially causing a slight short between it and the next wrap which results in a hotter coil and burnt hits. It's fairly obvious as the coil began to gunk heavily in ONLY the area immediately surrounding the welded section while the rest of the coil was relatively clean, but it still gave off a burnt flavor..
I tired to get a picture of this but my camera isn't good enough, but if you look into a stock head with a flash light look for a kink in the top wrap, that's where the weld is. If it looks like it's very close, or touching the wrap below it the extra metal on the weld might be touching the next wrap intermittently causing issues. If you are having burnt hits use a small screwdriver to pull up the nickle section of the wrap, it's very soft so it will move easily without distorting the rest of the coil. Now, if the weld on the bottom of the coil is the one causing problems you might need to re-wick as it's pretty hard to see down that deep in the head, let alone manipulate the coil.
The next can be causing the flooding I saw a few people mention. The negative coil lead exits downward like on most coil heads and gets secured between the center pin and the insulator. If the piece of wire sticking out the bottom goes out past the outer diameter of the center pin, when you screw the head in it will cause it to bind up with the base. This can cause resistance issues, the head not seating properly (and therefore the tank section not seating properly) as well as tweaking the entire coil inside the head, either causing burnt hits or flooding depending on how exactly it's tweaked.
I purposefully reproduced this by bending the wire outside the diameter of the center pin, and when screwing the head down tightly I looked inside with a light and saw that it was bending the coil to one side of the head, leaving a wick-gap on one side that caused flooding and causing several wraps on the other side to begin touching. You don't really need to re-wick to fix this, just use a small screw driver to fold the wire inward so that it won't interfere with anything when being tightened down.
Several new heads had the wire at the bottom sticking out to the side too far, so I made sure to bend them inward to avoid any future issues. It seems to be a good thing to check for before using a new head.
Now for the re-wicking pics:
The center pin comes out and the cap on the top can be pulled off with some pliers
The coil should then easily slide up out of the head casing:
Remove the old cotton, and then use a lighter/torch to burn off any gunk on the coil
I cut out a strip of cotton pad, wrapped it around the coil, and slid it back into the head. You might need to try it a few times to figure out the right amount of wick to use. I'd suggest splitting your pad and removing some of the fluffy inside stuff so that you have a thinner piece of pad, and have the fluffy inside part facing inward toward the coil.
While rewicking I made sure to spread the coil a bit more where the two NR leads are welded on to give some extra space to avoid potential shorts. To reassemble just insert the center pin to secure the bottom lead, and the top lead gets pinched by a notch in the top cap. To re-seat the top cap I'd suggest first pushing it on as tight as you can get it, then with the coil head screwed onto the base, and the base screwed onto something, push down with something like the flat-side of a pair of pliers in a rocking motion.
I also tried actually recoiling one before re-wicking it, but without using NR wire it's a pain to do. I used 27g Kanthal and the issue I kept running into was that when you trap the top lead with the cap it distorts the whole coil, because the Kanthal is a lot harder to get pressed into shape compared to the nickle. Might be able to do some really careful and specific bends in the wire to get it to trap without distorting the coil, but I gave up since it's much easier to just use the stock (torched) coil.
Hope this helps someone out there with their eGo one! I'm loving these tanks even more now that I know I can keep them running for a looong time, with a torch cleaned coil and new cotton I don't think I should have to buy new heads for a really long time. I am a bit disappointed with the hit-or-miss nature of replaceable coil heads, I currently have 4 tanks running, and have 7 heads that I've been using (I've been keeping a head dedicated to different flavors, and swapping them when changing flavors in the tank) of those 7 heads 2 of them gave me issues with dry hits and burnt flavor while chain vaping, which was localized to the wraps immediately surrounding the weld point.
