The short answer
A cold-tumbling Alliance is usually failing to prove airflow rather than failing to heat. Check the whole exhaust path, including the shared duct, before anything else. A loaded lint screen and compartment is second, a gas cock left closed after service third, and an ignition or flame-sensing fault last — and that one is an engineer's job.
What you observe
- The drum turns but never warms — Airflow has not been proved and the valve stays shut.
- Other machines on the same duct are weak too — The shared run is restricted.
- Lint packed behind the screen, not just on it — The compartment matters as much as the screen.
- It lights briefly and drops out — The flame is not being proved.
- NEAR MISS — a cool-down phase at cycle end — Designed behaviour, not a heating fault.
Causes, most likely first on this class
- Airflow not proved, so the gas valve never opens — First because it is the interlock that governs every gas cycle, and because on a shared duct the restriction can be somebody else's lint. The machine is healthy and refusing on purpose.
- Lint screen and compartment loaded — Second, and the part a site actually controls: a commercial machine fills its screen within hours, and the compartment behind it fills within days.
- Gas isolated at the machine cock or the manifold — Third: a bank is fed from a common gas train, and a cock closed for service is easy to leave closed. The machine runs perfectly and never lights.
- Ignition or flame-sensing fault — Last. Its tell is a machine that lights and drops out with a clear duct and open gas, and it must go to a qualified gas engineer.
Check in this order, and why
- Compare the machine against others on the same duct — Free, and it locates a shared restriction immediately.
- Clear the lint screen and the compartment behind it — The part the site owns, and the quickest win.
- Confirm the machine cock and manifold are open — Common after any service visit.
- Watch whether it lights at all, and for how long — Left until here because it only matters once air and gas are right.
What an owner can safely check
- Run a short cycle on two machines on the same duct — Weak heat across the bank points at the shared run.
About 45 min
- Pull the lint screen and vacuum the compartment behind it — Do this on every machine in the bank, not just one.
Tools: gloves, vacuumAbout 45 min
- Check the exhaust outlet outside is clear and unobstructed — Look for lint, nests, flap damage and crushed ducting.
Tools: torchAbout 30 min
- Confirm the machine gas cock is in its open position — Look only; do not disturb any gas fitting or joint.
Tools: torchAbout 10 min
- STOP HERE if it still will not light or holds no flame — Ignition and gas-train work is for a gas engineer.
Before you open anything
Safety
If you smell gas, do not operate any switch and do not touch the machine: leave the building and call the gas emergency number from outside. Otherwise isolate the machine at its disconnect and close its gas cock before opening any panel; a capacitor can hold a charge after the power is off. Never bypass the airflow interlock or a safety limit to force a machine to heat, and never work on the gas train yourself. Lint in a duct is a fire risk.
When to call a technician
Call a qualified gas engineer when the duct is clear, the screen and compartment are clean, the gas is open and the machine still will not light or will not hold a flame. Call a duct cleaning contractor first if a whole bank is weak, because that is a shared restriction and a fire risk. Leave the building and call the gas emergency number from outside if you smell gas.
Nearest pages of this class
What this page does not cover
This page is written for the brand and the appliance class, not for one family or model line. Where a family- or model-specific page exists for your unit, that page is the more specific answer and you should start there. Deliberately absent: gas pressures, duct sizes and lengths, ignition and valve part identifiers and fault-code meanings, all of which differ between the single-pocket, stacked and tumbler families.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
