WHAT IS CAUSING MY TOYOTA YARIS TO FORM ICE ON THE INSIDE?

Q I bought a new Toyota Yaris in November 2022. In January 2023 after a cold snap I complained to Toyota that the panoramic roof had ice inside which had to be scraped off or it would melt and drip on occupants. The dealer checked the car but could find nothing wrong. Recently the ice was back; again they couldn’t find a problem. Customer services confirmed that the dealer had found no sign of leaks and no other faults. What can I do?

– BN

A Icing on the inside of the panoramic roof is the result of a build-up of moisture inside the car. I would normally suggest that this is a result of a leak, but the dealer says that it has found no evidence of that.

That said, it couldn’t hurt to run a hose over the window, roof and windscreen seals to see whether you end up with damp carpets. It’s also a good idea to check the scuttle panel drainage holes for blockage, in case the dealer hasn’t been as fastidious as you might hope. If you find something, take the car straight to the dealer – it should be fixed under warranty.

If you can’t find a leak, however, there are a couple of other remedies. Firstly, cleaning the inside of the glass can help to reduce condensation. Use a common or garden window spray; if the condensation reoccurs, repeat the process a few times.

It’s also possible that the cabin air filter is clogged, although given that the problem first occurred when the car was only a few months old, I’d consider that less likely.

Finally, the extra condensation might be a result of the way you use the air-conditioning system. Firstly, make sure you aren’t using the recirculate function all the time – doing so retains all the humidity of your breath (and wet clothes) inside the car, which then condenses on to cold glass in the winter then freezes overnight.

You should also try running the air-conditioning constantly, if you are not doing this already; while it might be tempting to switch the system off to slightly improve the fuel economy in winter, doing so loses the drying effect of the air-conditioning, which can cause excess moisture to build up inside the car.