tsr
Established Member
Stopped engines are common on 171s too. There is or was at least one of the /8s out there which has been running with the engine automatically shutting down every few minutes... for months. For the last couple of years, at least, and up until now, these issues have not been causing many severe delays or cancellations in service... with the ex-170s no doubt this may change. The difference with the original Southern ones is that they will cross-feed so that you don't lose interlock (which is likely to happen whether or not the doors are locked) if you can only supply electrical power from half the coaches. Presumably it may be because of this that the interlock is able to be broken even if the coach is locked out of use and the engine isolated; it theoretically allows the train to detect a problem which has resulted in loss of interlock even if there is no electrical power originating in that coach, because the system should still be maintained by the supplies from another coach. I've needed to sort this sort of stuff out in practice on 171s, never actually to compare it to a 170 or ex-170, but this is how I've found it works and this is in line with what I was taught.
Perhaps a different way of phrasing it is that they don't realise that coach doesn't have problems being proven interlocked if there is no power but the doors are locked OOU. Doors are a funny thing on 171s, and assuming that what is vaguely normal with them also applies to anything else is probably a bit of an issue in and of itself...
As (very much) a side note, I also understand the buzzer on the 171/7 and /8 equates to a bell noise on the /2 and /4 (ex-170s). I wonder if there is also any difference to how the conductor proves interlock? The interlock light has never been functional with a conductor's key in the panel on a 171, and interlock is checked first by BIL lights all being extinguished, then by the panels' buzzer sounders only being activated when interlock is achieved... I'm wondering if any change has emerged, but I don't think any brief has gone out.
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