need help--HVAC Heater Control Valve problem

[psquared39]

Logic would say with the heater valve at full closed psoition it would be cutting off flow just like you are proposing to do manually, by capping each pipe. The cabin heater is a sub component of the engine cooling system, and engine cooling is not dependent on the cabin heating system. I would say it will affect nothing but the fact you wont have a cabin heater...