Here are the most common reasons:

Overheating and burning: T20 bulbs, especially halogen ones, generate heat. Over time, this heat can deteriorate the plastic connector material and the metal contacts, leading to oxidation or burning. This manifests as discoloration of the connector, "cooked" contacts, or even warping.

Loose contacts and interruptions: Wear, vibration, and exposure to the elements (humidity, temperature changes) can loosen or corrode the contacts inside the connector. This causes intermittent or permanent interruptions in the flow of current, causing the daytime running light to turn off or flicker.

Error messages on the dashboard: When the connector does not ensure proper contact or the bulb is not receiving the necessary current, the car's control unit detects an anomaly and displays an error message (e.g. "Check daytime running lights" or "Exterior lights failure") on the instrument panel.

Difficulty replacing the bulb: A damaged connector can make it difficult to insert or remove the bulb, increasing the risk of the bulb breaking or further damage to the connector.

LED Compatibility: If you decide to switch from halogen bulbs to LED bulbs for your daytime running lights, in some cases you may need to replace the connector or install additional resistors (error cancellers) to avoid compatibility issues with your car's electrical system and error messages.

Symptoms that indicate the need to replace the connector:

• The daytime running light does not come on or comes on only intermittently.
• The instrument panel reports an error relating to the daytime running lights.
• Excessive overheating is noticeable in the connector area.
• The connector shows visible signs of burning, melting, or oxidation.
• The bulb does not stay firmly in the connector.

In summary, replacing the T20 connector is often a necessary solution to restore correct functioning of the daytime running lights, eliminate error messages and ensure the safety and visibility of the vehicle.