Let us know if the flush fixes your problem. I have same thing going on with 94 STS, but just the opposite side. My drivers side footwell area has no heat, but passenger side does. I am not able to flush due to a ThermaGasket additive in my coolant that needs to stay there for another 200 miles. So watching for your results.CAD4DAD said:i have a 96 sts and the heater only blows out hot on 1 side of the car the drivers side, the passenger side blows out cold. this happens when i use the defroster also. what would cause this? and how do i fix it?