Dual-chamber disposables let one device deliver variety without doubling your SKU count. The trade-off is complexity: two heater paths, a selector mechanism, and more wiring packed into the same shell. One of the highest-frequency inbound problems is also one of the most expensive if it slips past receiving: one chamber fires normally while the other won’t heat. In practice, this defect can derail a fill plan, create rework queues, and trigger “mystery” complaints that are hard to trace back to a single batch once goods are mixed.

Within the runtz ecosystem, “2g dual chamber” hardware is commonly built around a 1ml + 1ml layout and a digital display, which makes the UI (and its chamber selection logic) part of your acceptance criteria, not an afterthought. If you’re receiving any runtz disposable dual-chamber shells, the workflow below helps you quickly classify the failure as a selection problem, a power delivery problem, or a heater/load problem—fast enough to run on an incoming sampling table.

1) Define the symptom (avoid false fails)

Teams often lump different defects under “one side not firing.” Separating them upfront makes your supplier feedback sharper and prevents you from chasing the wrong root cause:

• Type A — True no-heat: the channel never warms under any condition (even after a short charge).
• Type B — UI/selection mismatch: the device heats, but the indicator shows the wrong chamber, won’t switch, or switches unreliably.
• Type C — Intermittent: the channel heats only when pressed hard, tapped, or held at a certain angle (classic contact/solder strain behavior).

Incoming QC should log the type, carton/lot, and a short observation note (“B never heats; A OK; screen changes”), plus a quick video if the defect is intermittent.

2) Fast triage: three checks in under a minute

1. Confirm selection and mode: Toggle the chamber selector exactly as intended for that UI. On an LED screen vape, verify the display reliably changes state (A/B, left/right, flavor 1/2) and that the state is stable (no flicker, no random switching).
2. Confirm charge state: Low voltage can trigger protection earlier on one channel than the other if resistances differ. Retest after a short charge or with a known-good battery state (bench fixture if available).
3. Look for shipping stress: Dents near the bottom cap, seam gaps, a shifted window, or a loose switch are strong hints that the PCB or harness moved during transit.

2.5) Optional tools that make incoming QC faster

You can run the workflow with only your hands and eyes, but a few low-cost tools make your diagnosis faster and your supplier feedback harder to dispute:

• Digital multimeter: quick coil continuity/resistance checks (best signal for heater vs PCB).
• Magnifier + good lighting: catches hairline cracks, seam gaps, and screen window shifts.
• IR thermometer (or thermal sticker): confirms which side is actually heating when the UI is ambiguous.
• Simple test jig: holds the unit consistently so grip/pressure isn’t “part of the test.”

2.6) At-a-glance classification matrix

3) Know the architecture (so your tests mean something)

Most dual chamber disposable platforms share a common structure:

• One battery feeding a control PCB (power management + safety protections).
• Two heater circuits (two coils or atomizer modules), each driven by its own output stage (often a MOSFET channel).
• A selector input (button sequence, slider, touch, or firmware toggle) that commands the PCB to energize A or B.
• A shared UI stack (LEDs or screen) that reports battery and chamber state.

When one side works, you can usually assume the battery and the “main” PCB logic are alive. Your job is to determine whether the dead side is failing command (selector), delivery (output stage/wiring), or load (heater open/short). This is why the same defect can look totally different depending on whether you only do a “single puff” check or you test mode switching repeatedly.

4) Incoming-QC troubleshooting tree (field-friendly)

Step 1 — Prove whether switching is real

Do 10 toggles and short 1–2 second pulses. Use your fingers to feel for heat position (left/right) rather than trusting the screen alone.

• If heat always appears in the same physical location despite the UI changing, treat it as selector routing failure (Type B).
• If heat alternates correctly but the UI does not, treat it as UI mapping/screen board (still Type B, different subsystem).
• If switching works but one side truly never warms, continue to Step 2.

Step 2 — Screen for marginal contacts (quick stress tests)

Intermittent “one side dead” issues often come from cracked solder joints or a floating connector that passed factory test but fails after vibration.

• Tapping test: light taps on the shell while pulsing the “dead” side. If it fires after tapping, classify as Type C.
• Rattle + looseness: shake gently near your ear. Rattles correlate with PCB movement and harness strain.
• Switch feel: inconsistent tactile feel can indicate misalignment that also affects selector inputs.

When you see Type C, it’s usually a lot-level risk because the same mechanical weakness will exist across the carton. Escalate faster rather than “sorting” your way out of it.

Step 3 — Resistance test the dead channel (highest-signal check)

If you’re allowed limited teardown on a small sample (or you have factory test pads), coil resistance quickly separates heater failures from PCB failures. Compare against the “good” channel on the same unit.

• Open circuit: broken coil lead, failed weld, snapped flex, or connector not seated (common after shipping shock).
• Short: bridged solder, crushed coil, or contamination; protection often blocks firing to prevent overcurrent.
• Normal resistance but no heat: suspect output stage failure, selector input fault, or a harness break that opens under load.

Operator tip: Put the “good” and “bad” readings on the same line of your QC sheet. Trend differences across samples are more useful than absolute values.

Step 4 — Output-stage sanity check (voltage present or not)

If resistance is normal, the heater may never be receiving power. Where test points exist, check whether voltage appears across the heater during a firing pulse. No voltage typically indicates:

• a failed channel driver (MOSFET/output IC),
• a selector signal that never commands that channel, or
• a protection lockout triggered by a sensed fault.

Incoming QC isn’t component repair. The goal is to classify the defect so the factory can replace the PCB module, adjust assembly, or improve retention/pack-out.

Step 5 — Common one-side root causes (and what they imply)

• Heater lead/weld failure (A side open): assembly-process issue (weld parameters, fixture alignment, tab handling).
• Harness strain at bend points (intermittent): needs strain relief, better routing, or improved adhesive control.
• Channel driver failure (normal coil, no voltage): PCB-level issue; often requires tighter EOL test or better component screening.
• Selector/screen subassembly fault (won’t switch): UI path issue; treat selector + UI as one functional unit in testing.

On platforms that share a dedicated screen disposable subassembly, sample-test switching aggressively. A single “fires once” check misses the common failure mode: the selector works once, then becomes inconsistent after light handling.

5) A compact incoming QC SOP (copy/paste)

The SOP below is designed to catch the defect early without specialized fixtures:

1. Visual: seams, dents, window alignment, port integrity, obvious gaps.
2. UI reliability: wake + battery display, then 10 clean mode toggles (no missed inputs).
3. Functional per channel: three short pulses on A and three on B; confirm heat aligns with the selected chamber.
4. Intermittent screen: repeat the B test while changing grip/angle (no bending). Any behavior change = Type C.
5. Record: type (A/B/C), carton/lot, and a photo/video of the screen state + test action.

6) Quarantine rules: when to stop the line

Sorting can hide systemic issues. Use simple decision rules:

• Any Type C in the first sample set: quarantine the carton and expand sampling (intermittents usually scale).
• Repeated Type B (won’t switch): treat as a UI/selector lot defect; don’t assume “users won’t toggle.”
• Type A above your threshold: stop receiving and request factory investigation (heater/weld or PCB driver).

7) Supplier feedback packet (minimal, high impact)

To get a fast corrective action, send your supplier a short packet they can replay on their line:

• Failure type (A/B/C) + count by carton
• Repro steps (“toggle to B, pulse 2s ×3, no heat; toggle to A, heat OK”)
• Video showing the UI state while you test
• Any measurements you captured (coil resistance, “no voltage on B”)

This format reduces back-and-forth and helps the factory separate design issues (selector mapping/retention) from assembly issues (weld/solder/connector seating).