There are two equivalent versions of the PRS5 switch – 31302 (early) and 31448. There may be other suitable part numbers.

The Lucas PRS5 rotating switch is available in singe and double pole switching options. There are also two shaft-lengths available. I presume this is to allow for cars with either steel or thicker wooden dashboards. When looking for two position switches, the longer shafts may be cheaper. It is possible to find a shorter single pole version of these switches for even less and to exchange shafts between a pair of two-pole switches with little work. Alternatively, you can modify and exchange the short shaft of a single-pole switch into the housing from longer shaft switches as I have done.

Looking at the rear of the switch there are 5 or 6 terminals on the single and double pole switches, respectively. You can add a connector to the 1-pole housing at position 5 to convert it to two-pole switch after performing the modifications described below.

Both types of switch have a semi-circular cut-away at the end of the shaft where it locates in the Bakelite base. This cutaway limits the amount of rotation available when the knob is rotated. The single pole switches have shafts with extra material on the shaft. By removing material from the shaft, the single position switch can be converted to a two-position switch. The internal components are the same for all versions of the switch.

The switches are easily opened by gently bending the three sets of tabs around the base. After removing the knob, the metal housing will separate from the Bakelite base. You will see a rotating plate that has round brass lugs that is located by flats on the shaft. There is an insulating disc and a spring above this.

The shaft locates in a hole in the Bakelite and there is a semi-circular recess which limits the degree to which the shaft can turn because of the matching semi-circular section cutout on the shaft.

The switch components are shown at right with two of the electrical discs to show top and bottom. The single speed switch spindle is shown below.

The difference between the two switch types is shown below. The two-pole switch has a 180° angle. By removing the excess material from the shaft of a single pole switch, it can be converted to a two-pole switch.

As the workshop manual says, reverse the procedure to reassemble. The two-pole switch can be sired with the DR3 two-speed wiper motor, which looks almost the same as the original wiper motor.

See also article ET-219D on prior page for DR3 2-speed wiper motor.