Lucas Model P.L.C. 2. Lucas service number 344890.
Other than keeping the back of the unit clean and checking for frayed or loose wiring, no maintenance is necessary.
Erratic contact in the ignition and lighting switch is usually caused by the contacts becoming dirty or corroded - continued use may result in damage to the bakelite body.
The brass screws are often weak and the heads prone to rounding or snapping.
The Bakelite body may be badly burned if the switch has failed - it may be possible to scrape out the burned material and replace with body filler.
1) Label or colour-code any wires to the switch which might no longer be obvious.
2) In the centre of the back of the switch is a small brass nut - soldered in place. This can normally be undone without removing the solder, but if the stud begins to twist, the solder must be removed first.
3) Insert ignition key and turn slightly, then pull the key, barrel and retainer out.
4) The chrome front plate is secured by two "dogs", bent inwards to prevent the body from rotating. Bend gently outward to be parallel with the outer casing, taking care not to scar the front of the plate.
5) Twist and pull to remove the chrome front plate.
These switches are becoming scarce and expensive but since only the IG, T, A and H terminals are required, can be replaced by (for example) the body of a Lucas Model P.L.C. 6 without altering the outward appearance of the switch.
The P.L.C. 5 appears to consist of an identical front panel to the P.L.C. 2 and (probably) the same body as the P.L.C. 6.
Re-assembling the ignition switch is quite tricky - it is difficult to rotate the bayonet ring (the escutcheon plate) whilst applying pressure against the spring, to fit it all back together again. A solution might be to drill a 3/4" hole in a piece of 3/4" thick timber. Hammer two panel pins on a pitch circle, matching that of the contact wire screw holes, and leave the nail heads protruding by about 1/8" (to prevent the switch from rotating). The hole in the timber encloses the two center contacts and the flat surface allows force to be applied to the escutcheon plate, without applying excessive force to the terminals.
PLC5 and PLC6 switches are available from Vintage Spares Ltd. as part numbers #836A and #836 respectively.
None yet.