Solar street lights staying on during the day is usually caused by failures of the photoresistor, abnormalities in the controller, battery issues, or interference from external obstructions, resulting in malfunction of the light control system.

The photoresistor is responsible for sensing light changes: its resistance decreases in strong light, and the light should turn off; its resistance increases in weak light, and the light should turn on. If it is damaged or improperly installed (e.g., blocked), it may fail to respond correctly to light conditions, causing the light to turn on incorrectly during the day.

Solutions: Inspect and clean the photoresistor to ensure it is unobstructed and properly installed; replace it if damaged.

The controller is the core component that controls the switch based on photoresistor signals or voltage values. If its program malfunctions, components are damaged (e.g., burned MOS tube), or settings are incorrect, it may fail to cut off power during the day.

Solutions: Reconnect the controller wires; replace it with a matching model if the indicator light is off or functions abnormally.

When the solar panel is covered by snow, dust, or leaves, its output voltage decreases, which may trigger the controller to mistakenly judge "insufficient light" and turn on the light.

Solutions: Clean the surface of the solar panel; if the storage battery is not fully charged due to prolonged rainy weather, turn off the main power switch, place the light in direct sunlight to charge for 2-3 days, and then restart it.

Aging, damage, or reversed positive and negative connections of the storage battery can cause abnormal power supply and affect the controller's judgment; aging or disconnected wires may also lead to incorrect signal transmission.

Solutions: Check the battery voltage (normal full charge is approximately 13.8V) and replace faulty batteries; repair loose or damaged wires.

Hope this resolves the issue you're encountering.