Drvrs side blows cold, pass side blows warm even on high. No dual temp on truck. on 2003 Dodge Ram 3500

The truck blows super cold on the drivers side, but blows warm on the passenger side. What gives? I dont have dual air temps...just the normal stuff. I've only made one modification to the truck and added a K&N cold air intake. Any ideas before I drop some $$$ at a shop? Please, no smarts remarks...just some good advice. Thanks everyone!!

Asked by for the 2003 Dodge Ram 3500
2 answers
you could have a bad blend door or actuator under dash going out have it ck by your mech. very common issue with newer veh.
Service bulletin on blend door may apply to your truck ...not warranty unfortunately , and probably not a do-it-yourself job.