Considering the age of the 185s, they are some of the most inefficient heating and colling systems of any train I have been on.
Lets start with the system as a whole:
There are two sources of saloon heating in each car. There is the roof mounted Heating Ventilating Air Conditioning (HVAC) unit. This is the large thing on the roof you can see from the outside in the middle of each car. This blows out warm / cool / cold air depending on the temperature required. It only blows out at the ends of the coaches however - generally speaking the bits at the outer ends between the vestibules and the carriage ends. It is allegedly designed to ciculate around, but doesn't seem very good at doing so. This is due to the ducting in the roof.
Then there are the floor mounted electric radiators - these are the silver grills along the sides under the seats by your feet.
Now, the power for these features comes via an alternator on each engine.
Generally speaking, full heating capability is only available when all 3 engines are on. Why is this? Well, with one engine switched off there is no power coming to that coach from the alternator on that engine. It then "cross-feeds" (i.e. takes electrical power) from an adjacent car. However, there is not enough power available on 1 car to power every system on 2 cars. So, the car without an engine and the adjacent car which it is cross-feeding from both go into reduced power. The most noticeable thing is that the floor radiators do not work in both these cars in this situation. In the summer you notice that the cooling capability is significantly reduced.
Thus, with only 2 engines you have 2 cars with no floor radiators. And as the roof HVAC only blows out at the ends the middle of the coach will be cool at best.
This is the reason why the First Class is often the coldest part of the train - if either the 51 (DMC) or 53 (MS) cars have an engine out, then there will be no heating in First Class. (The 53 car when off always cross feeds from the 51 car).
The lack of an engine is not always due to eco-mode. A significant number of the problems are caused by isolated engines due to engine faults / awaiting parts etc. This is most obvious when travelling. If the same engine is switched off for a long time it is almost certainly isolated. In eco-mode the driver will normally start off from most stations with all 3 engines powered to give maximum power when getting to speed, climbing hills etc. When the eco-mode function switches off an engine automatically it will switch them off in rotation to get an even spread of fuel burn etc.
So, eco-mode and isolated engines aside why else is the heating poor?
The HVAC units seem to suffer from an incredible number of faults of various sorts (many argue this is due to the constantly fluctuation power supply caused by the constant switching on and off of engines). This means that in some situations - even with all 3 engines running - the HVAC unit in a certain coach will not put out any heat. This appears to be quite frequent. The result is that the HVAC will be blasting out freezing cold air - creating the arctic conditions described above. The experience on board is dire - it is not just cold, it is VERY cold - as it is not just a case of no heating, the HVAC is actually blowing out freezing cold air making it colder and more unpleasant.
Finally, there is the temperature set point. The temperature for winter was set at 20oC. This has now been increased to 22oC, which is better - and noticeably so. If you have a unit with all 3 engines on all the time, and no HVAC faults, it is noticeably warmer and more comfortable than before.
On train crew have no control over these functions - all the heating / cooling functions are automatic - and need a laptop plugged into the central saloon roof section - to reset or alter.
Finally - 170s. Generally 170s are far better, and in 8 out of 10 situations the only faults are minor and can be reset by the Guard to clear the fault.
