BA-4 Heater
The gas-electric heater Eberspächer BA4 came as standard equipment on all VW Type 4s. It was necessitated by the simple fact that the old-style heat-exchangers, a design taken over from beetle engines and enlarged, could not handle the passenger compartment size.
The BA4 enables the driver to not only heat the air coming out of the standard heat exchangers a lot further, it also acts as a stand-alone unit which can be used to pre-heat the passenger compartment, even without the engine running. This is done with a timer built into the main dashboard switch which can be set to run the heater unattended for up to ten minutes.
Volkswagen provided their dealers with a comprehensive workshop manual for the BA4, reproduced here.