Coil build step by step, work order and ohm checks

A failed coil build rarely gives itself away at the moment it goes wrong. The coil looks tidy, the screws are tight, and the fault only shows at the first press of the fire button, when the mod rejects the atomiser or a bright red spot flares up in the middle of the wraps. More often than not, the mistake dates back several steps, and nothing could reveal it without a check made at the right moment.

The coil build in seven steps and five readings

A good coil build always follows the same order, and most of its steps end with a resistance reading. A deck ohm reader, or the screen of a regulated mod that measures resistance, runs through the whole job like a common thread.

Work out the expected value and cut the wire to length.
Wrap the coil on the jig, with contact or spaced wraps.
Seat the coil on the deck, tighten the screws, then take the first reading.
Trim the legs flush with the terminals, then take the second reading.
Dry fire gradually to clear hot spots, then take the third reading once the wire has cooled.
Wick the coil, then take the fourth reading.
Close the atomiser and read the value on the mod before the first draw.

Each reading in the coil build is compared with the one before. As long as the value stays stable and close to the calculation, you carry on. The moment it jumps, you stop at the current step, because that is where the fault lies.

Setting up the bench before cutting any wire

The kit fits in a small case. You need a coil jig with calibrated rods, or failing that a smooth rod of known diameter, flush cutters that trim close, fine-nose pliers to guide the legs, insulated ceramic tweezers, a screwdriver that fits the deck screws and an ohm reader.

The wire is chosen before the cutters come out. Our reference build uses 0.40 mm kanthal A1, and our guide to kanthal gauges and diameters explains why we think in millimetres rather than AWG numbers.

Next comes the length. For six wraps on a 3 mm rod with 5 mm legs, the coil wire meter on the workshop’s home page gives 74.1 mm per coil, or 148.2 mm for a dual build. Cut a few centimetres extra to hold the wire while you wrap, and the surplus goes when the legs are trimmed.

All that remains is to note the target. With this wire and this geometry, the six wraps come to 0.74 Ω, the figure every reading in this coil build will be measured against.

Contact or spaced wraps, decide before you wrap

Both ways of wrapping give almost the same resistance, but not the same coil. The choice is made before you touch the jig, because it changes the width of the build and how you dry fire it afterwards.

Contact wraps

Each turn sits against the one before. The coil is compact, 2.4 mm wide for six wraps of 0.40 mm, and fits narrow decks. The trade-off is a dry fire that needs care so the glow spreads across every wrap.

Wrap with light tension on the wire so the turns close up without overlapping. A wrap riding on its neighbour can be seen with the naked eye and is put right before the coil goes on the deck, never after.

Spaced wraps

Here you leave a gap of roughly one wire diameter between turns. Vaping360 notes that slightly spaced coils generally show no hot spots, which makes the dry fire simpler.

Spacing hardly changes the resistance. With a 0.8 mm pitch, each wrap grows by just 0.03 mm, under 0.3%. It does change the width, which rises to about 4.4 mm for six wraps. Check that this width fits between the terminals on your deck.

Seating the coil on the deck without bending it

How the coil is seated decides how well the build holds. Slide the legs into the terminals with the jig rod still inside the coil, then tighten the screws one after the other. The rod stops the coil twisting as the screws bite, a common fault at this stage.

Then centre the coil over the airflow and check it touches neither the deck nor the base of the terminals. Take the first reading here. The value should be stable and sit a little above 0.74 Ω, because the length of leg between the coil and each screw adds 0.0115 Ω per millimetre.

Now trim the legs flush with the terminals. A stub of wire left proud will sooner or later meet the chimney or chamber and cause a short. Take the second reading straight after trimming. The wire you cut sat beyond the screws, outside the circuit, so the value should match the first reading. If it moves, the cutters have shifted the coil.

Gradual dry firing to flush out hot spots

The first firing is done dry, with no cotton, starting low. The build guide published by the French retailer Taklope says 10 to 15 W is usually enough to make a high-resistance coil glow. Step up in small increments if nothing lights, never all at once.

Give short pulses and watch where the glow starts. A sound coil glows from the centre outwards, evenly. A patch brighter than the rest is a hot spot, often an uneven gap between two wraps or a bent wrap. Between pulses, gently pinch or comb the coil with the ceramic tweezers, then go again.

Once the glow is even, let the coil cool and take the third reading. On kanthal, whose resistance barely changes with temperature, the value should return to what it was before the dry fire. A clear difference points to a wrap that has moved or a screw that has worked loose.

The final coil build reading before you vape

Cotton goes in only once the coil heats evenly. As it slides through, the wick can push the wraps and nudge the coil towards the deck. Hence the fourth reading, taken with the cotton in place, which should repeat the third.

Finally, close the atomiser and screw it onto the mod. The value on screen should match the ohm reader, give or take a small difference, and fall within the range your mod and batteries accept. If everything agrees, the build is ready. If not, open it up and work back through the readings to find the step at fault.

FAQ

Five questions that come up on a first build, and that the walk-through above doesn’t cover.

What is a series coil build?

Two coils joined end to end, so the current passes through one and then the other. Their resistances add up, so two 0.74 Ω coils give 1.48 Ω. In parallel, the usual arrangement on dual-coil decks, the same pair drops to 0.37 Ω.

What is a Clapton coil?

A wire made of a core, an ordinary resistance wire, with a much finer wire wrapped around it in a spiral. It is built like plain wire, but its resistance is harder to work out on paper, which makes the ohm reading all the more important.

How do you deal with coil gunk?

Remove the cotton, then dry fire the coil in short pulses to burn off the deposit, a practice described by Vapebeat. Let it cool before rewicking. When the deposit won’t shift, building a fresh coil takes less time than fighting the old one.

Do you need a coil jig, or will a plain rod do?

A smooth rod of known diameter is enough for a single coil. For a dual build, a jig helps you produce two identical coils, and that matters, because two different coils in parallel don’t share the current equally.

Why don’t the mod and the ohm reader show the same value?

The mod measures through its 510 connector and the atomiser’s pin, the ohm reader directly at the deck. A small difference is nothing unusual. A bigger gap points to a loose pin or a dirty connector, worth checking before you vape.

A coil build is judged by its readings, not its looks

A neat coil can hide a wrap that touches, and a crooked one can work perfectly. Only the readings settle it, and they cost a few seconds at each step. Getting a coil build right is mostly a matter of reading the ohm reader at the right moment and stopping as soon as the value jumps.

The wrapping technique will come with practice. The work order applies from your very first build and holds for every deck, from a single coil to the busiest dual build.

Also on the bench

Build notes from L’Atelier Brouillard, for adult readers only. Vaping products usually contain nicotine, which is addictive, and nicotine vaping products are not for sale to under-18s in the UK. Nothing here is a recommendation to buy.