2003 Kia Optima blower motor won't turn on. with ac on I turn on blower fan and ac turns off. ac works, blower fan works, replaced fan switch and theramal resister in air duct and did not solve proble

are there any relays?

are the relays located under the hood with the other fuses, if so I checked all 3 that were named cond. fan lo, cond. fan hi-1 and cond. fan hi-2. I checked for continuity across 2 posts out of the 4 on each, they all had continuity.

they did not smell burnt?

take off the ground connection battery to the frame, clean it with a wirebrush to assure we are getting solid ground to the chassis...also to the engine...am going to tell you must be on your second battery at least, if not, this could be the source of your problem...battery is old but still does the job...like pushin' grandpa across the street~

you've got insufficient amperage...'tis the source of the problem~

The relays on my kia don't smell burnt. Battery is good no problems.the only thing not working is the blower fan switch. when I turn it on the ac turns off and the fan does not start.

I would argue that it is NOT fine, based on the age of the battery 2003 makes this one ready for the scrappel~...because a car battery will stop accepting a charge approximately ten percent per year....so after ten years it's workin' on "fumes" as it were---not to mention that when they get this old they command FULL output from your alternator/voltage regulator...so if your battery has been replaced inside of five years...you're okay~ an aggressive "LOAD TEST" by dead shorting the battery (under controlled circumstances) for three seconds...then check if it still will pull the startermotor, then see how many hours it takes to charge back up....your, I'm afraid will not survive this aggressive test~.....because it can't take a charge anymore.~