I am constantly amazed at how much you seem to know about these old girls! Do you have one there or is it all in your head?

G-CPTN worked for Bedford for a while so he knows quite a lot, and what he doesn't know (not much!) he researches.

17 years as an Experimental Vehicle Design and Test Engineer.

For the benefit of others working on TKs, this is my understanding of the primary air supply system based on the discussion in this thread.

There are two pressure switches for low air pressure (one of which was not connected) that are in the two lines between the footbrake valve and the servo. Surely these lines see low pressure most of the time (except when the driver has his foot on the brake) so what are the switches for? I wonder if they are in series with the brake light circuit?

From where you describe the position of these switches I would say they are stop light switches.

I wish I wasn't so dim sometimes! That explains it perfectly; the low air pressure switch for the buzzer must be somewhere else, probably in the cab near the emergency brake release valve.

Sorry I can't help you with that one - I last worked on a T.K about 30 years ago and I just can't remember.

There will be at least two - one for each reservoir.

Sorry - I cannot identify the locations (electrician's job), at a guess look inside the chassis side-rails.

I'm fairly certain that they aren't an integral part of the gauges - but I'm not 100% sure.

I think it was only on later vehicles that the switches were incorporated in the gauges G-C. I remember the first time I came across them I was pulling my hair out trying to find them.