I had a look in my LT Routemaster workshop manual but being a 1964 edition it significantly pre-dates assault alarms. I can actually remember how the assault alarm was first shown to union reps by a prototype fitted to RM 8 which visited garages to a schedule so that the union rep would be awaiting its arrival. Over the course of a couple of weeks it visited over sixty garages and I just happened to be in Tottenham Garage when it arrived which, I`m guessing, was around the Summer of 1975.

I don`t know about the availability of heater motors or the ease of refurbishing. But there are many who visit this site and have knowledge of such things - and possibly may have the Alteration Advice paperwork which would have been produced to acquaint garage staff with assault alarms.