Reverse light switch for 3- and 4-synchro pre- rod-change transmissions. This switch replaces the plug on the front of the remote shift transmission case, and is triggered internally by the shift linkage when reverse is selected. It is used with an insulating fibre washer (originally 2K7914) and actuated by a small plunger (22G351) below it in the gearbox. Ref: 39889, GAE131.
Make sure you are using 3cm long 2A3647 detent spring (8.8mm wide); using a smaller-diameter spring pushes the switch detent plunger in all of the time causing seizure, closure or jamming of switch.
See 36557 for rod change version.
Note that washer 1B3664 can be used as a substitute, though the internal hole is slightly larger than the original.