Carriage pre-heaters ex-classes 15/25

I was looking at a photograph of a former class 15 locomotive used as a train pre-heater at Stratford, and noticed that one of the train description headlights had been relabelled "heat on".

When they were modified into this role, did they remain self-propelled or was the engine used solely to power a steam boiler and/or electric generator, and were they coupled to a train with the aid of a shunting engine?

Similarly, what was the situation with the class 25 ETHEL units?

 

I think the ETHELs were isolated. http://www.derbysulzers.com/97250.html

 

Couldn't provide traction .The bogies currently under D8233 have no traction motors .

 

That would seem to answer my question - so another locomotive would move the pre-heating unit to the stock. Next question; could the class 15s provide steam and electricity for heating, or only one?

 

Eth d8233.org.uk

 

Thank you for that, my questions are answered

 

Yes in the case of the ex-25s at least that is what the ETH in ETHEL stood for. If memory serves me correctly Electric Train Heat Ex-Locomotive

 

The class 15s had everything that wasn't necessary ripped out, so there were no electrical machines, no air ducting etc etc.