[ukrkoz]

let me put it this way:
heater core inlets are directly going through the firewall.
heater core hoses are directly connected to the heater core inlets inside the engine bay
there are no vlaves or such anywhere on the hoses, they go straight into the pump/core.
ther a ppear to be no vlaves on the heater core of any nature.
i have just checked.
haynes does not mention/picture any valves.
if it's blowing hor with climate control on cold, probabaly your climate control unit. appears to be all electrically controlled, most likely - electric actuators, maybe vaccum though i doubt, on ducts doors.