Hi folks!, I did a pretty extensive search, and I'm not seeing exactly my situation, but several close ones.
I've noticed that the AC / Heating system on my 1997 XJR X300 has an issue by blowing Heat in passenger side vent and Cold in driver and even the (middle) center vents blow half heat and half cold, by changing the temperature I can see the difference in the driver side but nothing on the passenger! and my car has Solo climate control,
Thinking about heater core being plugged or probably blend-door issue.

So please tell me where to start the diagnosis.

Rabeea

 

The heater solenoid valve could be stuck open. It's the valve hooked up to the auxilary water pump next to the brake booster. If it is stuck open, then hot fluid will flow continuously through the heater core.

 

its possible that a blend door is stuck,those doors are in the dash and are controled electricly...steve.