Since carb rebuild, van idling high only when cabin fan is on???????

[Billabong]

91 Suzuki Every 660 (DB51V) - help!???
Ok, so we rebuild the carb last week, put everything back exactly where it goes. It's idling high... only when the cabin fan (for hot/cold/ac) is on??? What the @#$!@#? I never noticed if it was doing this before so I don't understand what the heck is going on now. My dad (a retired mechanic) helped me out with all this and has come down to one hypothesis; when the fan is on (makes no difference if it's on low, medium or high) the van is thinking the ac is going to be working so it's increasing the revs to accomadate the ac compressor. Does any of this make any sense to anyone out there? Thank you in advance for any help and thank you all for all the knowledge you have all shared on this board.

ps - we can adjust the carb using the bolt on the side but not when the fan is on...

My dad's question; why the hell does it speed up when I turn the fan on?

[Billabong]

Found out how to correct the problem. There is a screw towards the back of the truck (mid mounted engine) right near the gas wire that has to be adjusted.