Why does our car always have misty windows?

My wife has a 2013 Nissan Micra and finds in certain conditions that the windows severely mist up, even on a dry day. We have checked there are no damp carpets, no damp patches under the spare wheel nor under the scuttle and we had the pollen filter changed. The problem is partly cured with the windows open and heater on, or even using the 'on/off ' air conditioning, but the rear windows remain misted. Could there be a vent that may be blocked?

Asked on 29 January 2020 by Michael Greenhalgh

Answered by Dan Powell
The air conditioning should never be switched off. It's designed to be used in conjunction with the heating system at all times (not just in the summer). Turning the A/C off for long periods will cause the joints to dry out and allow the coolant gas to escape. It also increases the risk of the compressor seizing up. If the windows are clean and there are no obvious drainage blockages, I imagine misting is being caused by faulty air conditioning. It probably requires a regas.
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