Heater only blowing hot air

[PD_GT3]

As the title, the next saga in my high mile SD story is this, the heater only blows (very) hot air, I've looked but can't find any other people with a similar issue, any idea's guys?

Thanks,

Paul

[Nuclear Nick]

Ferdie had this back in the summer on his 911. It resolved itself after a short while and AFAIK it hasn't happened since.