In summer, I prefer to use the 150s/153s if I can, more opening windows. I don't find the 4 windows in 158 carriages do a great job regulating temperature (but obviously would rather have them open when aircon is faulty).
I wonder if it will be much the same when the 166s arrive. Mind you, replacing 25-30 year old trains with 25 year old trains, I'm not expecting every problem to be solved. Would be good if the 158s'/166s' aircons do get sorted though. It's been long overdue.
Often if the air conditioning is not working properly then it is blowing out warm air, which can be why having the windows open on a 158 doesn't help as much. I found that to be the case with a 166 last year, which was much warmer than a 165 I'd travelled on just before it.
