no...not really ,but when it comes time for summer your a/c system may not be as cold .i just replaced mine twice this year .first time it self destructed in the driveway and second time was last week when i had to track down some vac problems and noticed the valve was installed wrong but it leaked around the pivit arm .
the valve close's off the coolant flowing through the heater core by way of a vac solinoid ,when closed it allows the internal vent inside the cabin to close and bypass's the coolant. i noticed on mine before it was not working the heat would bleed through into the cabin on any slide setting ...like max a/c setting .when working properly it activates the door to shut and cutting off heat but also it cuts the coolant going into the heater core.
hope that was not to confuseing ....... but like i said before should not really hurt anything except getting a little to hot in the cabin in summer temps .
hope this helps
