Electrical failure due to water infiltration in the BSM (Engine Module)

• Most affected models: C3 (generation 2003 to 2012) and Xsara Picasso.
• What happens: The car starts exhibiting “phantom malfunctions” (wipers turn on by themselves, headlights flicker, the engine shuts off unexpectedly, or the car simply won’t start).

What to check:

1. The barbecue drains: Open the hood and look just below the windshield. That’s where the drains that carry away rainwater are located. Leaves and debris often clog these channels.
2. The BSM lid: The black box that houses the fuses in the engine. Check if it is cracked, poorly fitted, or has signs of water/moisture inside.
3. Corrosion on fuses: Remove the main fuses and check if the pins are greenish or whitish.

Solution:

• Preventive: Clean the grill drains regularly (simply pour water and push the accumulated dirt against the sides so that the water flows freely to the ground). Fit the BSM lid correctly.
• Corrective: If water has already gotten in, disconnect the battery, remove the BSM, apply a quick-drying electrical contact cleaner to the entire board and fuses. If the module’s internal traces have already burned out due to a short circuit, bench repair by an electrician or replacement of the part will be necessary.