As is usual for any vehicle that has a few years behind it, the electrics are “interesting” to say the least. Generations of mechanics have practiced their crimping techniques on the wiring!
We found the original wiring diagram in a 1949 Commer workshop manual but it has been modified (several times).
1949 wiring diagram for a petrol Commer 5 and 7 ton “forward control” truck. No computers here!
The original didn’t have such luxuries as windscreen washer, indicators, two stop and tail lamps or two dip headlights (the manual says that “for home market only the left hand headlamp has a dip beam but for the export market both headlamps have dip beam”)! These have been added in our vehicle along with dual headlights on each side (one dip, one main). The vehicle has also been converted from positive earth to negative earth and several switches have been remoted onto the steering column.
The tangled mess of wiring and crimps.
Ignition and lighting switch
The first job was to replace the ignition and lighting switch. It was very intermittent in both of its main functions and had been attacked with the soldering iron several times in the past as can be seen from the picture.
A “pattern part” was obtained but this proved to be wholly unsuitable and basically disintegrated on first use(!); an original “new old stock” replacement was eventually sourced and fitted after swapping the lock barrel over (as the replacement comes without a lock).
On the steering column there is the usual stalk switch for the indicators on the right side (although this also seems to have been remoted at some point).
Another stalk was fitted on the left side but had been broken off sometime during a previous life. We had worked out that it was something to do with the headlights but without a proper wiring diagram we were guessing somewhat.
Pressing the test meter into use showed that one wire was connected to the main beam headlights and the other to the dip beam headlights(!). This was a little odd as we already have one of the floor-mounted press switches for the main/dip beam switching.
We decided on a slight modification to allow it to function as a “headlight flash” as this is very useful and not easy to do with the existing lighting switch and floor switch.
The dip-beam wire was reconnected to the permanent power fuse (that runs the horn and cab lights) and a suitable biased switch was obtained. Unfortunately the housing cover was damaged along with the stalk but this was repaired with some Isopon, sanded down and painted black.
The new switch and the repaired housing cover before painting.
The completed switch fitted to the old housing. This also shows some of the switches that have been remoted from the dashboard.