Automotive maintenance: causes of window fogging and diesel filter issues

Vehicle owners face various maintenance challenges ranging from cabin moisture to diesel particulate filter malfunctions. Window fogging is often caused by more than just a dirty cabin filter. Moisture can accumulate in wet floor mats, snow on the glass, or water leaking through door seals and clogged drainage channels. A sweet smell or oily residue on the glass may indicate a leaking heating system radiator. To combat fogging, drivers should ensure floor mats are dry, check seals, and use fresh air intake instead of air recirculation.

In certain diesel vehicles, particularly those from French manufacturers like the PSA Group, the diesel particulate filter (FAP) relies on a specialized liquid additive stored in a separate tank. This additive, often based on cerium or iron, allows the filter to regenerate at lower temperatures, which is beneficial for city driving. If this additive tank runs empty, the regeneration process becomes ineffective, leading to a clogged filter even if no other mechanical failures are present. Newer models often utilize catalytic coatings to avoid the need for this additive system.