How we handle cabin filter replacement at Hackbridge
The interesting part of this job is not the filter, it is what surrounds it. With the housing open we look for leaf litter and silt, standing water, and the tide mark that says water has been sitting there for some time. On cars where the filter lives under the scuttle at the base of the windscreen, that area drains through a pair of small channels which block with leaf mulch, especially on a car parked under trees. Blocked drains send the water somewhere else, and on a good number of cars somewhere else turns out to be the passenger footwell or a module mounted beneath it.
The new filter goes in the right way up, with the airflow arrow pointing the way the car pushes air, and seated so the frame meets the housing all the way round. A filter a few millimetres undersize, or one forced in at an angle, lets air take the easy route past it, which is why bargain filters sometimes seem to change nothing. Afterwards we run the blower through every speed and check flow at the face vents, the screen and the footwells, because a restriction further downstream feels identical from the driver's seat. If the evaporator behind it smells, or the drain is plugged, we say so rather than selling you another filter.
We will not fit a filter into a housing with water standing in it and call the job done, and we will not sell an air conditioning treatment as a cure for a smell that is coming from a blocked drain. If the filter was changed recently and is still clean, we will tell you and charge you nothing. The price depends entirely on how long it takes to reach, and your registration gives us that before you book, so you know in advance whether you are looking at the starting figure or an hour of labour.