I used a single valve on mine, it has 4 hose fittings on it so, it will bypass your heater core. It is vacuum operated so it is easy to turn on or off. We get plenty warm in the summer during the day but sometimes it is a bit chilly in the morning or evening an a bit of heat is nice. Or if it rains and I want the heat on for the defroster.
Napa 660-1294
