Why does my air con sometimes blow warm air?

My Ford Transit Custom's air con is cold, but sometimes goes warm. There's no pattern to it. It's had a new relay and regas. When it's warm the fan isn't running, what could the issue be?

Asked on 5 July 2018 by Mick

Answered by Honest John
Might need a fresh pollen filter, otherwise you can be asking too much of the fan to suck air through a clogged filter.
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