Proper HVAC vacuum hose size and source

[tucsonjwt]

Does anyone know the proper size for the vacuum lines used in the HVAC system under the dash in my 83 C20? I put the calipers on the O.D of the tube for one of the vacuum actuators and got 3.63 mm/.143". So, would this be 3.5 or 3 mm for all of the vacuum lines under the dash? And where do you find this tiny line? All of the parts stores around here just stock the larger under hood sizes. I need the hose from the HVAC vacuum canister under the hood to the actuator for the blend door, then to the HVAC vacuum valve by the HVAC control (+who know what else is under there.) Thanks.