I have an LG dishwasher model LSDF9969BD that will not always turn on when the power button is pushed. This problem is very sporadic, sometimes if I wait about 10 hours it will turn on, sometimes it will not. Once it does turn on it runs through the cycles just fine as it should. The only symptom of the problem is that it won’t always turn on when the power button is pressed.
Sometimes when it doesn’t turn on for me, it will turn on in the middle of the night just randomly.
It seems to have power from the house. I turned the breaker off at the electrical panel and let it sit for about 30 minutes and then turn it back on. When I do turn the breaker back on I do see a light on the dishwasher control panel turn on very briefly. Turning the power off at the house electrical panel doesn’t seem to impact whether or not I can turn the power on at the dishwasher.
Since it’s such a sporadic problem, I don’t see how it could be the noise filter or the control panel. Is there anybody out there that has seen this or have any recommendations for me to test?
Brand: LG Model Number: LSDF9969BD Main Symptom: Not powering on What happens & when:
Error Code (if any): None
Parts or tests already tried: Resetting breaker in house electrical panel
Photos / video link:
1. Failing power supply on the main control board (most likely)
LG boards contain a small switching power supply that is energized all the time. If components (usually electrolytic capacitors, startup resistors, or the power supply IC) begin failing, the board can:
Fail to boot when power is present.
Suddenly come alive hours later.
Work perfectly once it finally starts.
Flash briefly when power is restored at the breaker (exactly what you’re seeing).
This is a very common failure mode in electronic appliances.
The fact that it sometimes wakes up in the middle of the night is a classic symptom of a marginal power supply that finally reaches the correct startup voltage.
2. Loose or burned connection where house power enters
Before replacing electronics, inspect:
Junction box under the dishwasher
Wire nuts
Terminal block
Harness connector going into the noise filter
A connection can be making intermittent contact.
Look for:
brown insulation
melted plastic
darkened terminals
3. Noise filter (line filter)
You mentioned you don’t think it’s the noise filter because it’s intermittent.
Actually, they can fail intermittently.
Inside is a thermal fuse and filtering components. I’ve seen LG and Bosch filters where vibration or temperature changes cause intermittent output.
An easy test:
When the dishwasher refuses to power on, measure:
120 VAC into the filter
120 VAC out of the filter
If power is entering but not leaving, replace the filter.
4. Door latch switch (less likely)
Normally a bad door switch causes:
dishwasher powers on
display works
won’t start
It doesn’t usually make the entire display dead, so I don’t think this is your issue.
5. User interface/control panel (possible but less likely)
A failing touch panel can ignore the Power button.
However, this doesn’t explain:
randomly powering on by itself
brief flash when breaker is restored
Those symptoms point more toward the main control board than the keypad.
Things I would test
Step 1
When it refuses to turn on:
Measure voltage at the main control board.
You should have approximately 120 VAC present.
If you do not, work backwards:
junction box
noise filter
wiring harness
Step 2
If 120 VAC is present on the control board while the display is dead:
Replace the main PCB.
Step 3
While the failure is occurring, gently:
wiggle the connectors
tap lightly on the control board housing
If the dishwasher suddenly wakes up, you’ve found either:
cracked solder joint
failing relay
failing power supply
One thing you mentioned that really stands out
“When I restore the breaker I briefly see a light on the control panel.”
That tells me:
AC power is reaching the machine.
The control board attempts to start.
It immediately shuts back down.
That is exactly what happens when the low-voltage supply on the control board cannot sustain startup.
My diagnosis (from most to least likely)
Main control board power supply failure
Intermittent noise filter☆
Loose wiring/connector in the power input circuit ☆☆
Touch panel/UI board ☆☆☆
Door switch ☆☆☆☆
One question that would help narrow it down:
When the dishwasher is “dead,” is there any LED lit at all (even a dim one), or is the display completely black with no response whatsoever? Also, do you have a multimeter available to check for 120 VAC at the control board and the noise filter?
A tiny crack or separation in the user interface (especially around the button membrane, display window, or housing seam) can allow moisture or steam to enter the control panel. Because the dishwasher environment is warm and humid, even a very small opening can let condensation accumulate over time. Once moisture reaches the printed circuit board, it can cause:
Corrosion of the switch contacts or PCB traces.
Increased electrical resistance, making buttons (often the power button first) intermittent or non-responsive.
Short circuits between traces.
Permanent damage to the tactile switch or membrane contacts.
The fact that replacing the user interface resolved the issue strongly suggests the control board itself was still functional and the failure was isolated to the UI assembly.
If you’re documenting failures or speaking with the manufacturer, you could describe it like this:
“A small crack developed in the user interface housing that was not readily visible. The crack allowed moisture intrusion into the control panel, resulting in corrosion of the power button contacts. The user interface eventually became inoperative and had to be replaced.”
It’s also worth noting that this is a different failure mechanism from a software or electronic defect—it’s a moisture ingress issue caused by a loss of the enclosure’s seal. Even hairline cracks that are difficult to see can eventually lead to this kind of damage in a high-humidity appliance like a dishwasher.
