1972 wiring diagram
- Thread starter pierodn
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pierodn said:
White/purple connects the ballast resistor to both the coil negative (-) terminals.
For whatever reason, the colour code [WP] does not appear on the wiring diagram. :roll:
This wiring should be under the fuel tank. As you said "under the saddle" if there is also a WP harness wire running back to the battery compartment area, then its terminal should be isolated.
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That purple and white wire you described is also paired with a white and red wire (WR). Believe it or not, your Norton is wired for a starter motor. The wires under your seat would have gone to a starter solenoid. The white and purple wire would have been the ballast resistor bypass for starting while the solenoid was engaged. One thing I don't understand myself is that the white and red wire goes to a terminal just ahead of the carburetor and then another white and red wire continues from the carburetor area to the wire branch under your seat. I just have no idea what would connect to those white and red wires. My 1974 Norton Commando has the same wires you described as well.
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PeterJoe said:
The white/red would have operated the starter solenoid from the push button on the handlebar switch cluster with the white/red wire.
pierodn said:
The factory intended to fit a starter motor to the Commando from 1971, that's why those wires are in the harness, however the starter motor drive proved to be too fragile, so the starter was never fitted and a blanking plate (often incorrectly referred to as a magneto blanking plate) covered the hole in the rear of the timing chest where the motor would have been.
The 850 MkIII starter was a completely different system.
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pierodn said:
Nothing to do with the Electra.
I think perhaps you have misunderstood? The factory intended to fit Commandos with starter motors from around 1971 (either as standard or as an optional extra?) however the electric starter system proved to be too unreliable so it never went into production, and no electric starters were fitted until the 850 MkIII, that's why the blanking plate is there and why the solenoid wires are often included in the harness, and it would most likely have been the reason why the factory fitted a ballast resistor and two 6V coils from 1971 in place of the previous two 12V coils (and no ballast/R) used up until that time.
This is a drawing of the original Commando starter motor assembly that was never used:
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I am convinced that is exactly why the ballast resistor was put in the Norton Commandos. The factory service manual under Ballast Resistor (with 6 volt coil 1971 and later models) quotes:L.A.B. said:
"This permits the use of 6 volt coils in an otherwise 12 volt system. The 2 coils are wired in parallel with the resistor in series. When the battery voltage is dropped due to heavy current taken such as by the use of an electric starter, the ignition coils are fed direct, by passing the resistor and thus enabling the coils to work at their approximate potential. "
I can only guess why Norton used the 6 volt coils and ballast resistor. One possibility is that they had a contractual agreement with Lucas and promised to purchase all of those 6 volt coils and ballast resistors. Maybe they had hopes of coming out with an electric starting Commando throughout the following years. Someone out there probably knows the real reason. It's too bad that the original starter motor arrangement didn't work out for Norton.
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