Mystery Road Light switch on late XK 120 OTS

XK
1

Have been trying to find the Lucas number of the “Road Light Switch” used in the late XK 120 OTS dashboard with Jaguar code C.8395 used from about March/April 1954 till end of production.
The SPC specifies Jaguar part number C.8396 (new switch apparently coded together with new dashboard C.8395) as a PRS.7 type switch, however without any Lucas number. On my April 1954 built XK 120 OTS SE I found the original light switch (see photo) with…well… no Lucas number.

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All previous XK 120 versions had the Lucas 31387/A which is a PRS.5 switch. Looking at the underside of my switch this is a typical PRS.7 switch (like the SPC refers to). See photo.

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Been searching for more information and found that Jaguar code C.8396 is also used on the late XK 120 DHC models where the SPC refers to a Lucas switch 31428/A meaning problem solved or not???

Lucas specifies that switch 31428/A is a “rotary three way” switch (fully correct) with a short bush and only one nut for mounting. But my C.8396 switch has a long bush with 2 nuts.

The XK 140 used a PRS.7 “Road Light Switch” C.5577 (so much earlier than C.8396 !!!) with Lucas number 31426/A which has a long bush with 2 nuts. So problem solved or not? Looking at the picture of C.5577 in “Jaguar XK 140 Explored” (plate 7-d1) the underside looks identical apart from the fact that this switch has only 3 screws whereas mine has four.

Can anyone confirm that the underside of my switch is identical to the underside of C.5577 (Lucas 31426/A)? If so, we’ve solved the mystery and apparently Jaguar started using the XK 140 light switch already at the end of the XK 120 production. But then the question remains why Jaguar didn’t use the already exiting part number C.5577? Or is the extra screw the difference between the two?

Leaves us with the question whether later DHC’s (using the same number C.8396) also had the 31426/A instead of the 31428/A switch and Jaguar made a mistake in the SPC …

Bob K.

2

Bob,

My 140 dhc has the long bush with two nuts but has no apparent part number. It has six cheese head screw terminals in three pairs spaced equally.

Eric

3

As described above, later XK 120’s used a PRS.7 type of Light Switch (versus the PRS.5 type on the earlier versions).

To complete the information about this change of switch, we have to add that also the Escutcheon changed which is not mentioned in the relevant SPC’s. Fortunately some of the suppliers know this and can provide the correct Escutcheon. But don’t use the numbers of the XK 120 SPC’s for these later versions as they are simply incorrect. This applies to the information in XK 120 Explored as well.

The earlier XK 120’s used Escutcheon C.2762 (Lucas 304802) with the text OFF, S and H,

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Later XK 120’s had Escutcheon C.8165 (Lucas 30568) with marking O, S and H and as you will see the positions of the letters also changed, due to the different construction of the PRS.7 switch (with 30 degree steps) compared to the PRS.5 switch type (with 45 degree steps)…

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The latter Escutcheon was continued on the XK 140 (except for Special Equipment versions with Fog Lights),

Bob K.

4

Thanks Bob, this is very timely for me, as I am restoring two escutcheons, one for the 120 and adding one to the Mark V, which was missing for 54 years. So I finally learned the reason for that hole above my light switch, its for the locating peg on the escutcheon. It is held in by spring fingers on the center sleeve.
I found a sheet of white 1/8" lettering decals used by the model railroading hobby. I will make them both OFF - S - H.
My SS and Mark V have the boat rudder handle, but we can’t forget the Tee handle version.

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