I recently travelled on a heritage 15 to Tower Hill. I was pleased that the bus was nice and warm with an outside temperature of only 3ºC. There was a good flow of warm air into the upper and lower saloons through the original air ducts, even when stationary. This suggests that a fan had been added to the air flow system, probably during its 2001 Marshall Bus refurbishment.

I wondered if anyone knew how this had been done as I was considering copying the idea for my RMs. RM471 had heated air blowers under seats on both decks when it worked in Glasgow in the 1980s but they weren’t working and I removed them, and the coolant pipe work to them, when we put a rebuilt AV590 in two years ago.

My bus number (if any): RM471 & RM 2213

The Marshall refurbs had several mods for heating carried out but the fans are two small units mounted in the heater matrix box at the front. This mod works very well and all the heritage RMs are always warm and rarely steamed up during the cold months.
On an original set up a non-stop 30 mph run was the only way to warm a bus through! Even in 1959 that was going to be a rare occurrence in London!!

Even in my LT days, I could not fathom out who thought a ram air heating system on a stop start slow moving vehicle was a good idea. In my view, the heating system was really poor on the RM and being alloy bodied, a colder space to heat anyway, I was amazed a program of retro fit RT style heaters was never implemented especially on country buses.

The best post LT mod was the heaters.