The heating system on air-cooled Volkswagen vehicles includes the heater boxes (part of the exhaust manifolds), the heater control cables, the heater channels (or center tube on type 2 models) and the cooling fan. The heating system is ingenious in its design and functions as follows:
The cooling fan not only blows air over the engine to cool it down, but also blows air through hoses into the back end of the heater boxes. The boses are designed to allow the incoming air to pass over the hot exhaust pipes, thereby absorbing heat. The heated air then exits out the front of the heater boxes, through connecting hoses to the heater channels or center tube. The heater channels, found on type 1 and 3 models, run along the rocker panel of the vehicle, whereas the center tube on type 2 models is routed up the center of the Transporter body. The heated air travels up the heater channels/center tube and can exit at a number of openings (at the rear seat, the front seat or up at the windshield for defrosting purposes). The control flaps, which dictate at which opening the air exists, are controlled by cables and knobs.
The heater channels are often a problem spot in the heating system, because they rust and become obstructed. Welding is required for heater channel installation and is better left to a professional automotive body technician.
For the removal and installation of the heater control cables, refer to the following procedure.