Nissan Civilian Bus Convesion

Don't know whether the Nissan is the same but on the Toyota's there is a switch either on the dash or the wiper stalk to turn it on or off. It is activated by a switch on the accelerator pedal which in turn activates the solenoid etc.
Does the actuator work when you liftoff the go pedal? does the actual butterfly operate freely in the exhaust?
Usually it is a mechanical problem rather than electrical, most common is the butterfly jamming due to exhaust buildup in the pipe.

Thanks Peter, for your reply but I have cheeked that, they have a separate lever on the opposite side of the blinkers which seams to be working OK, the butterfly is working but the Spring seams to be real strong one would think it would lose it's pressure over time from heat but it certainly hasn't could be the problem but who knows I might have to look in this area it has 30 psi of vacuum which should be enough ? Thanks Charlie.

I know it sounds stupid but make sure the idle knob is turned down. Ive done it myself took me 20 min to work out what was wrong with it Cheers Tony

Thanks Tony, no the idle is spot on, I have checked every think the micro switchers are working it is just some thing, when it stops raining I will go & pull the butterfly box off it again & start from there, Thanks Charlie.

Thanks Pop, I will check it out any idea what vacuum pressure it should have at the
valve ? Thanks Charlie.