A dryer heats air, passes it through the drum, and carries the moisture out of the building. Everything depends on that last part, and it is the part nobody looks at.
What restriction does
Restrict the exhaust and the wet air stays in the drum. Clothes stop drying, so the cycle runs longer, so the element runs longer, so the cabinet runs hotter than the design allows. Eventually a thermal cutout opens to protect the machine and you have a drum that turns with no heat in it.
People replace the cutout. It survives until the next long load, because nothing that opened it has been dealt with. We see this more than once a week.
Working out where the restriction is
The lint screen, obviously, but also the screen itself. Dryer sheets leave a film you cannot see. Run water on the screen; if it pools rather than passing through, wash it with hot water and a brush.
The duct behind the machine. Rigid or semi-rigid metal, never vinyl, and as few bends as the room allows. Pushing a dryer flat against the wall crushes the duct into exactly the restriction you are trying to clear.
The full run and the exterior hood. In a single-family house this is yours and it wants cleaning every couple of years. In a townhouse it may be twenty feet with four bends. Go outside while the dryer runs and put your hand at the hood; if there is barely any air, you have found it.
The situation people do not expect
In some of the condominium buildings up here every apartment feeds into one shared riser with a booster fan at the roof. Your lint is not the only lint in that duct, a booster problem shows up in your apartment as a slow dryer, and none of it is yours to clean. The tell is a machine that tests perfectly: element good, thermostats good, airflow good at the machine, drying time still terrible. At that point you need the management company, and we will tell you so rather than sell you a part.
The one that is not about drying time
A burning smell during a cycle means stop the machine. Lint against an element is a fire rather than an inconvenience, and that is a same-day call.
Call (847) 555-0142.
