That can depend on the route which may have short platforms or if its quiet the Guard will sometimes lock the rear set out of use. The connection is often open on the trains I've been on. At times Northern use a passenger train to attach an empty set to in order to save an ECS path and crew later on. Another possibility is a defective gangway door catch or lock which means the door either won't open or won't stay open (the front door is very thick and heavy).
When a 150/2 is working in multiple with other stock the connecting end cab door is open to passengers. Is this in multiple with all stock or just 150/156?
Does the fore mentioned cab end door have normal controls to open and close the door or does it just open automatically when the doors are released?
Well it wouldn't be if the 150/2 was attached to unit without corridor connectors like a 142, 150/1 or a 170.
Does the fore mentioned cab end door have normal controls to open and close the door or does it just open automatically when the doors are released?
I am refurring to the single leaf doors. They certainly work with a 150/1. I saw it myself on the Harrogate line.
The single leaf door on a 150/2 will release for passenger use when that door is next to an intermediate cab regardless of there being a corridor connection to the adjacent unit.
If you mean the single leaf door on a 150/2 then yes a Guards panel is located at this door in a locked cabinet. When it is at the intermediate position (ie the coupled cab) the doors release for passenger operation as per the other doors, the only time the passenger buttons on a 150/2 single leaf door don't energise is when they are at the end of the train.
Does the fore mentioned cab end door have normal controls to open and close the door or does it just open automatically when the doors are released?
Believe they should work when at the back of the train, it's only the doors behind the leading cab that won't be energised, but even they should be available for use from the inside.
Could be wrong but I read this as referring not to the crew doors but to the end gangway doors, i.e. the doors through which one would walk from one unit to the other? In which case, these doors are manually operated and locked either open or closed. The door which would usually close off the whole cab from the interior of the train swings over to seal off the Driver's side, and the gangway end door and hinged folding 'fly screen' (the flithy yellow bit!) swings over to seal off the other side of the cab, thus allowing access through the nose end gangway of the train. All gangway-fitted 15X Sprinter units are compatible and will usually have through access when in multiple, but obviously if there's a 150/1 or 142/3/4 in there then the gangway and cab stays closed.
I too took the OP to mean the gangway door but then the single leaf local door was mentioned.
