JP wrote:
Ridership does not seem to be a problem, but reliability of the 165
fleet, whilst hitting a peak a few months ago has again slumped to
around half that achieved by the Reading based examples. ATP problems
perhaps? The Chiltern 165s do have a few extra bits on them which
would mean more to fail. The Chiltern engineering staff are looking at
some innovations which have caught the attention of other DMU
operators, all of which would go a long way to improving reliability.

Could it simply be down to a bit of over-zealous fault reporting? Certainly
I can't recall the last time that I encountered a Chiltern 165/0 operated
service that was cancelled or that was a failure in traffic (it's been 168s,
if anything). Similarly, I can't recall the last time that I found a 165
with defective air-cooling in any vehicle in the set or was on a set that
had door problems - in fact I can't think of any instance in the last year.
Conversely, your 165/1s don't have air-cooling to worry about and, IME, on
the 166s I've found it quite common to find a vehicle in traffic with the
air-con not working, even on my infrequent GWML inner-suburban journeys.