It must be the start of summer here in the UK, because the temperature has hit 26° C for the last couple of days. The downside is that the air conditioning in my car can’t cope with it at all. Last year it seemed fine. My initial diagnosis is leaking heater valves, which mean that engine coolant is always going through the heater matrix even with the valves closed.
I’ve bought a new heater valve unit (photo to follow…) and hopefully I’ll find the time to fit it this weekend.