The short answer
A Cosmo dishwasher that does nothing when you press start is far more often a supply or a door-latch problem than a failed board. Under a kitchen sink the supply comes through an outlet or a junction box that shares its life with a disposer and a lot of moisture. Check power and latch before anything else.
What you are actually seeing
- The panel is completely dark and no button responds — Means: on-page
- The panel lights but the cycle never begins — Means: on-page
- The machine beeps once and stops — Means: on-page
- The door will not latch fully — Means: on-page
- A delay start or control lock is showing on the display — Means: on-page
- The cycle starts and then stops partway through — Means: different-fault — Go to: cosmo-dishwasher-cycle-fault
- The breaker trips when the machine is switched on — Means: different-fault — Go to: cosmo-dishwasher-electrical-safety
- Body: Match what you see before you take anything apart. The panel is completely dark and no button responds. The panel lights but the cycle never begins. The machine beeps once and stops. The door will not latch fully. A delay start or control lock is showing on the display. Some near-miss symptoms belong on a different page: The cycle starts and then stops partway through points at a cycle-progression fault rather than a start fault, covered on cosmo-dishwasher-cycle-fault; The breaker trips when the machine is switched on points at an electrical fault to stop using the machine over, covered on cosmo-dishwasher-electrical-safety.
Causes, ranked for this machine
- No power at the outlet or junction box under the sink, or a tripped breaker or GFCI — Why this rank: First because the supply under a sink is the most disturbed circuit in the kitchen: disposers, water and cleaning all happen there
- The door is not latching hard enough for the interlock to make — Why this rank: The interlock is what allows a cycle to begin, and a slightly proud rack or a misaligned strike stops it without any obvious symptom
- Control lock, delay start or a demonstration mode left set — Why this rank: These survive a power cycle on many controls and owners rarely remember setting them
- The water supply valve under the sink is closed, so the machine waits and appears dead — Why this rank: A machine waiting for water can look like a machine that never started
- A failed door latch switch or control board — Why this rank: Last because it needs a part and the four causes above it are free to rule out
- Body: Ranked for a built-in kitchen dishwasher with an electronic control, a manual filter and a drain hose running to a disposer or an air gap. Most likely: No power at the outlet or junction box under the sink, or a tripped breaker or GFCI. First because the supply under a sink is the most disturbed circuit in the kitchen: disposers, water and cleaning all happen there. Next most likely: The door is not latching hard enough for the interlock to make. The interlock is what allows a cycle to begin, and a slightly proud rack or a misaligned strike stops it without any obvious symptom. Third: Control lock, delay start or a demonstration mode left set. These survive a power cycle on many controls and owners rarely remember setting them. Fourth: The water supply valve under the sink is closed, so the machine waits and appears dead. A machine waiting for water can look like a machine that never started. Fifth: A failed door latch switch or control board. Last because it needs a part and the four causes above it are free to rule out.
What to check, in order
- Confirm power at the outlet under the sink, and check the breaker and any GFCI
- Push the door firmly closed until the latch seats and press start again
- Clear any control lock or delay start with a full power-down at the breaker
- Open the water supply valve under the sink fully
- Body: Each check rules out the causes above it. First, confirm power at the outlet under the sink, and check the breaker and any GFCI. Second, push the door firmly closed until the latch seats and press start again. Third, clear any control lock or delay start with a full power-down at the breaker. Fourth, open the water supply valve under the sink fully.
Checks you can safely make yourself
- Switch the breaker off and on once, then wait and press start again to see whether the control wakes — Tools: none — Time estimate: a quarter of an hour
- Open the cabinet under the sink, find the outlet or junction box feeding the machine and test the outlet with a lamp if it is accessible — Tools: lamp, torch — Time estimate: a quarter of an hour
- Push the lower rack fully in, close the door slowly until you hear the latch seat, then press start while holding it closed — Tools: none — Time estimate: a few minutes
- Read the control panel for a lock symbol or a delay indicator and clear it according to the panel markings — Tools: none — Time estimate: a few minutes
- Trace the water line under the sink to its shut-off valve and confirm it is fully open — Tools: torch — Time estimate: a few minutes
- Body: Checks an owner can make with the machine switched off at the breaker, or by watching a cycle. Step one: Switch the breaker off and on once, then wait and press start again to see whether the control wakes. Tools: none. Time: a quarter of an hour. Step two: Open the cabinet under the sink, find the outlet or junction box feeding the machine and test the outlet with a lamp if it is accessible. Tools: lamp, torch. Time: a quarter of an hour. Step three: Push the lower rack fully in, close the door slowly until you hear the latch seat, then press start while holding it closed. Tools: none. Time: a few minutes. Step four: Read the control panel for a lock symbol or a delay indicator and clear it according to the panel markings. Tools: none. Time: a few minutes. Step five: Trace the water line under the sink to its shut-off valve and confirm it is fully open. Tools: torch. Time: a few minutes.
Safety first
Safety
Switch the machine off at the breaker before reaching behind it or opening any junction box under the sink, and never bypass or tape the door latch. Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. unplug-before-service
Where the owner fix ends
Call a technician when the supply is proven live, the breaker holds, the door latches audibly, no lock is set and the water valve is open, and the machine is still dead. The remaining causes are the latch switch and the control board, both behind a panel with mains terminals.
Nearest pages of the same kind
Generalized information
This page is generalized across the Cosmo dishwasher line. Front-control and top-control machines, and panel-ready and stainless fronts, share the ranking above but not every part, and this page does not cover a specific model or control revision. Family- and model-specific pages, where they exist, are linked below.
Links: - [Common COSMO Dishwasher Problems](/blog/cosmo-dishwasher-problems) - [COSMO Dishwasher: Abnormal Noise or Vibration](/blog/cosmo-dishwasher-abnormal-noise) - [COSMO Dishwasher: Does Not Clean or Dry](/blog/cosmo-dishwasher-cleaning-performance) - [COSMO Dishwasher: Controls, Display or Error Code](/blog/cosmo-dishwasher-control-fault)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
