Originally Posted by CR94
Originally Posted by Trav
... If it doesn't have what was commonly referred to as a Ranco valve you can fit one easily, it will improve A/C performance on older cars that may have a leaky blend door ...
Hmm... I wonder if lack of a shut-off valve, a leaky blend door, or some other form of heat leakage might be why my Prius blows warmer than outdoor air when heat and AC are both supposed to be off. It's very annoying in mild weather. My brother has the same complaint with his '95 Avalon. My Mazda had a proper coolant shut-off valve AND blend-door temperature control.
Quite possible. The easy way to tell is use a thermometer in the vent on full A/C, disconnect the heater core and put a connector in between the 2 hoses (or a piece of hose to the 2 block connections) so you can run the engine, if the temp at the vent drops you have your answer.
Install a valve before the core.