That's not a switch. It's an air valve with an adjustable pressure regulator next to it that it's feeding. The picture appears to be rotated 90 degrees and it's a little too tight to see the other stuff around it but I'd hazard a guess since it looks to be right below the squirrel cage radiator blower outlet into the engine compartment (it blows down) and sucks air in through the side radiators. The belt that drives the upper fan pulley attached to the double-ended gearbox that drives the squirrel cage blower(s) is air pressure tensioned with a pneumatic cylinder and that switch/valve is used to dump the air to the tensioner so the belt will relax and you can change it easy peasy. At least that's what I think it is. A better pic showing the overall engine and compartment would be helpful. Those valves were positioned in a couple different places through the years so I may be off on what that one is, but the A/C belt had one too. But I guess that's all been removed, the Bus A/C system machinery I mean.Thanks Steve. I'll have a look. Another couple for ya: what does this switch do and what does this hose go to? Both are back by the engine...
Who knows what that hose is, I may even be from the removed A/C, if of course it's really been removed. A pic of the engine area will tell me a lot.
I noticed something interesting suggesting that engine is a pure mechanical and not a DDEC controlled engine. I'm not sure from the pic but I see a couple air actuators which usually are associated with the governor for fast idle and one looks like it may be a shutdown actuator but I can't see the governor housing. Another pic of that area might help.
Your mission now is to reverse engineer and figure out what the **** the previous guy was thinking and were he might have put stuff....like pumps and such. That's the giant thing I have against dealing with anybody else's conversion. We all have our vision, but others may not execute it well at all, or the vision sucks. Take you pick. It looks generally pretty good overall you just need to figure out where it all is, catch up to it and make it eventually all yours.
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