1. Coolant leak: If the coolant system has a leak, the steam from the coolant can enter the cabin and cause the windscreen to steam up. Check for any leaks in the coolant hoses, radiator, water pump, or thermostat housing.
2. Faulty heater core: If the heater core is faulty or clogged, it can restrict the flow of warm air into the cabin. This can cause the windscreen to steam up as the warm air condenses on the cold surface of the glass.
3. Blocked cabin air filter: A blocked cabin air filter can restrict the flow of fresh air into the cabin. This can cause the air inside the car to become humid, which can lead to the windscreen steaming up.
4. Faulty air conditioning: If the air conditioning system is not working properly, it may not be able to dehumidify the air in the cabin effectively. This can cause the windscreen to steam up, especially on humid days.
5. Faulty door or window seals: If the door or window seals are damaged or worn, it can allow moisture to enter the cabin. This moisture can cause the windscreen to steam up, especially when it rains.
6. Damp or wet carpets or upholstery: If the carpets or upholstery in the car are damp or wet, it can increase the humidity level in the cabin. This can lead to the windscreen steaming up.
7. Too many passengers: If there are too many passengers in the car, the combined body heat and moisture from breathing can increase the humidity level in the cabin and cause the windscreen to steam up.
8. Using the "recirculation" air setting: Using the "recirculation" air setting can trap humid air inside the cabin, leading to the windscreen steaming up. It's generally advisable to use the fresh air setting to circulate outside air into the car and dehumidify it.
