I have a 1998 Dodge grand caravan 3.8l with 264K miles on it. Runs great. The van has dual heat control. The rear heater lines rusted out and I bypass the rear heater completely. I get good heat out of the driver side floor and dash vents but only cold air out of the passenger side floor and vents. Does the passenger side have a seperate heater core which I might have bypassed also or do I look elsewhere.