this might sound crazy but it could be your a/c belt...

well if you have a/c

but this is just a theory but on the chevy astro and some of there other vehicles when the defroster is on the a/c pump is working to pull condensation out of the air so the windshield clears quicker....

but im not even sure kia sportages do this....just trying to get the brain juices flowin and keeping this thread on top so someone who knows what they are talking about can respond

<a href="www.pittsfieldcustomsclub.com/sportage.html" target="_blank">98 sportage</a>: warn manual hubs,upyourkia spacers, 104 tj springs, 235/75/r15 BFG T/A KO, tracker rims, cone air filter, custom cat-back with a skunk2 muffler. gonna be a 2.3L