A downdraft vent that keeps humming away well after you’ve shut it off, or that seemingly runs on its own, points to a fairly narrow set of causes because the blower motor and its control sit close together beneath the cooktop.
Step 1: Rule Out a Stuck Control
Touch-slide or button controls exposed to spilled liquid or grease film can occasionally register as continuously pressed. Wipe the control area thoroughly and try cycling the fan off again.
Step 2: Check for Residual Heat Sensing
Some downdraft systems tie fan speed to a heat sensor near the cooktop surface, running the blower a bit longer after high-heat cooking to help clear residual smoke. This is intentional and should taper off within a few minutes, not run indefinitely.
Step 3: Power Cycle at the Breaker
If the fan won’t stop through the normal controls, switching off power at the breaker for a minute and restoring it resolves a genuine share of control-board glitches.
Step 4: When It’s the Relay, Not the Control
If the blower still runs continuously after a power cycle, the control relay that switches power to the motor has likely stuck closed and needs replacement — not something to leave running for days while you decide on a repair.
Visit our JennAir cooktop repair page to book a visit.