Thanx RGunther,
That makes sense.
By the way I tried the Idle up switch yesterday on the 185 and it does not cut out after engaging gears. I have to push the "on switch again" to stop it.

The Idle up switch on my bus dosen't have a two way rocker switch ie down "on" up "off". It is a sprung switch that has one function "on" push "on" again and it turns "off".

Shane