I'm not sure if this procedure applies to other makes..but for many Daihatsus (mine is an s83) the air filter box intake has a summer and winter setting.it needs to be changed manually ..there is a vacuum controlled flap in the air inlet on top of the filterbox that is closed in normal operation to bypass fresh air,for preheated air from the warming hose around the exhaust...this is the winter setting...in summer you don't need preheated air (or in warmer climates) and the vacuum hose needs to be blocked off so fresh cool air can get in. Takes all of 30 seconds and can be done without removing the engine cover..I removed the cover for a clearer pic.
Cool!... Er... Hot! Mine was controled by,ugh, donno, but i hated it so i ripped it out! We see low temps in winter here of about 42F =D But if i ever take it up to flag staff on a camping trip in winter i may be sorry, they can see minus F temps easy. Just have to hang a hair dryer on the snorkle in the morning. Good post, i would not asume that was manual and be confused as heck if i ran into problems.
Dragging up an old post but the time of year makes it relevant to possible new members who may not be aware of this. I made a quick video of the changeover http://www.youtube.com/watch?v=BnwgjYFu6iU
