Red warning light stays on while riding — 1969 Commando Fastback 750

L

Lorenzo

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Hi everyone,
I have a 1969 Norton Commando Fastback 750 and I've noticed that the red warning light on the headlight stays on both when the bike is stationary and while riding. The bike has been fitted with a Boyer Bransden electronic ignition replacing the original points, but the rest of the electrical system is original — no Boyer Power Box has been fitted.

I have always understood that on this specific year the red light is simply an ignition warning light and is not connected to any charging indicator function — so it staying on may be normal for this model.
Can anyone confirm what the red light on a 1969 Fastback is actually wired to? Is it purely an ignition light, a charge warning, or something else? And should it go out once the engine is running?

Any advice from those with experience of early Commandos would be very much appreciated.
Many thanks
 
Edit: I default to Les's correction.


That light is controlled by the assimilator, which monitors AC voltage from the stator.

You could have:
1) a faulty assimilator
2) broken wires from the stator
3) faulty stator
4) faulty rotor.

TEST, don't guess.

Do you have a voltage meter to test the AC voltage?
Are you familiar how to use it?
 
Last edited:
APRRSV said:
I thought the Hi beam warning light was green.
Click to expand...
No, not pre-71, 38189 (99-0568) is red.
andover-norton.co.uk

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
Red warning light stays on while riding — 1969 Commando Fastback 750
Haven't we done this one before.
A

Post in thread 'I'm a newbie wishing to know what I have. (2013)'

Wasn't the pre-71 Commando warning light green. It was a high beam indicator as I remember.

Ed
 
Last edited:
L.A.B. said:
A 1969 model doesn't have the assimilator, the red warning light pre-1971 is for main/Hi beam. It should be connected to blue/white and red.

andover-norton.co.uk

Andover Norton - WARNING LIGHT, RED, HEXAGON LENS (38189) - 99.0568

WARNING LIGHT, RED, HEXAGON LENS (38189)
andover-norton.co.uk

Red warning light stays on while riding — 1969 Commando Fastback 750
Click to expand...
it seems the red light is always on, no matter if the lights are on, main or high beam or off at all.. BTW I noticed that the speedo bulb is blown, but not sure if this is the reason of wrong functioning..
 
Yes one side of the light should be connected to the headlamp high beam wire (blue/white) and the other side to earth/ground (red) so it should only be on when the high beam is on.
 

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