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Unfortunately, the currently available replacement headlight switch (VW p/n 211 941 531e) for early bay buses (1968 - 1973) no longer have a terminal #57, and the correct switch is NLA. This terminal was used to illuminate a green dash indicator when the switch was pulled out to the first position (parking lights only). While this is not a critical function, it's nice to have.
There is a workaround. Obtain a standard Bosch cube relay. The current rating isn't important - the lowest capacity available is fine, as the dash indicator only draws around 250 ma. Wire the relay as shown below:
The wire used doesn't have to be very big - 22 AWG is fine. Make the wires around 6 inches long. Crimp female 1/4" blade terminals to the wires going to the relay. Crimp female 1/4" piggyback blade terminals to the wires going to the headlight switch (this way, you simply unplug the existing wires going to terminals 56 and 58, plug on the new piggyback terminals, then plug the original wires back onto the new terminals. Makes for a neat installation. When wired, tie-wrap the relay to the headlight harness wires to keep it up out of the way.
The circuit works like this: when the headlight switch is pulled out to the first position, terminal 58 has voltage on it (lighting the parking and tail lights), but terminal 56 does not. This applies power to the relay coil, as its resistance is an order of magnitude greater than the unlight headlights it's in series with, and thus all of the voltage drop is across the relay. When the relay activates, it applies power to the green dash indicator, causing it to illuminate.
When the headlight switch is pulled out to the second position, power is applied to both terminals 58 and 56 (lighting the headlights). At this point, the relay has power applied to both ends of its coil, which results in no voltage drop across it. The relay deactivates, turning off the green dash indicator.
There is an anomaly with this emulation, but it's not really a problem: on buses which have an "X" terminal wire coming from the ignition switch, if the ignition key is off, the green indicator will light in both headlight switch positions (because there is no headlight power to turn the relay off). Now if your ignition switch doesn't have the "X" wire, and you've connected the headlight switch "X" terminal to a nearby 30 terminal, then this anomaly won't occur.