I noticed one or two concerns on your forums regarding nasty niffs created by a bacterial build-up on the air conditioning evaporator. We have some experience of this and investigated alternative treatments extensively as the products we had used previously were ceasing to be effective. We conclude that this is for two reasons: Bacteria develop a resistance to certain products and access to the evaporator itself has become more difficult. In most German vehicles it is secured in a sealed box with the heater matrix and is not usually visible. Japanese vehicles have a separate evaporator thus encouraging airflow around it and discouraging bacterial growth in the first place. In the worst cases bacteria flow through the vents causes nausea, headaches and a runny nose. There is a product marketed by Wurth, this is rather like the old smoke machines that atomise a liquid product through the recirculation flap in the passenger footwell. We have used this for three years now with 100% success. The process takes about 45 minutes combined with an a/c service. The alternative options seem very hit and miss, bombs leave a residue and aerosols may or may not get it depending on where the bacteria are developing. We looked at about a dozen or so alternatives before taking this (the most expensive ) option. Wurth is so sure of its atomised sterilisation product it is supported with a 12-month guarantee.