If your dryer hums but the drum sits dead still, the drive belt is almost certainly snapped. That is the cause on the large majority of these calls. The idler pulley is next in line. Both are repairable, and we can usually confirm the diagnosis and finish the repair in one visit.
Why the drum stops turning
Broken drive belt. The belt is a long rubber loop that wraps the drum, runs under the idler pulley, and ties to the motor. When it snaps, the motor keeps humming but nothing drives the drum. You might hear a soft thump at startup, or nothing at all. One check you can do right now: open the door and spin the drum by hand. If it turns free with almost no resistance, the belt is gone.
Seized or worn idler pulley. The idler keeps tension on the belt. When the bearing inside wears out, the belt slips or wears through faster. A failing idler usually squeals before it quits.
Drum rollers, glides, or rear bearing. If the drum feels stiff or grinds when you spin it, the cause is probably worn drum rollers, glides (the pads supporting the front of the drum), or a rear bearing. They create enough drag that even a good belt cannot turn the drum. That is a different repair than a belt swap.
Motor drive pulley. Less common, but the small pulley on the motor shaft can wear smooth or crack on older machines.
What we check
The hand-spin test is always first. Open the door, spin the drum, note the resistance. Spins free with no tension, that is a broken belt. Grinds or feels stiff, that is worn rollers, glides, or a bearing, and the diagnosis goes deeper than the belt.
With the cabinet open, a snapped belt is usually obvious. It sits loose in a coil at the bottom of the cabinet. A worn belt may still be in place but cracked, glazed, or fraying at the edges. We check the idler by hand for roughness and wobble. If it is worn, it comes out with the belt. Replacing both at once is standard, because they wear together and the labor is already done.
One thing worth knowing: a failed door switch can cut power to the drum motor entirely. If the motor is audibly humming, the door switch is fine and is not your problem.
Why this is a pro job
Reaching the belt means opening the cabinet, pulling screws and retaining clips, then physically supporting the drum while you thread the new belt under the idler and around the motor shaft. The routing has to be exact. A twisted or misrouted belt snaps again fast or runs loud. Samsung and LG front-loaders take more disassembly than most platforms and leave less room for error.
More important, we inspect the idler, drum rollers, glides, and bearing while the machine is open. If those are worn, you want to know now, not on a second service call two months later. On a machine that is eight to ten years old, that full drivetrain check tells you whether the repair makes sense at all. Parts and labor vary by brand and model, so we give you the number after the $75 diagnostic, credited to the repair, before any work starts.
Call us
If your drum will not turn, we can usually get out same or next day across the Bay Area. Straight diagnosis, honest answer on whether the repair is worth it. Call (925) 999-4095 or schedule a visit.