Norton Commando Workshop Manual

## Electrical

# J

Relays
Standard 6Ra continuously rated relays are used. These should be so positioned that the cables carrying the horn current are as short as possible.
Technical Data

Frequency of Notes | 438-495 Hz
Ratio of Notes | 8 : 9
Sound Intensity | 90 dB at 50 ft. (15.24 m)
Cycle of Signal | 1-1.2 Hz
Power Consumption | 60 watts

Testing Procedure
If the horns do not sound when the switch is operated, check the voltage at the HC 3 control as follows:
1 | Connect a voltmeter, red lead to the cable removed from the +ve terminal, black lead to the cable removed from the - ve terminal. Operate switch, voltmeter should read the nominal voltage of the system.
If the voltage is satisfactory at the control unit proceed to check the individual horns and relays separate from the control unit as follows:
1 | Remove leads from one "R" terminal and the + ve terminal on the control unit and join together. Operate switch, the relay should be energised and the associated horn should sound, if satisfactory.

2 | Repeat above operation by joining together the leads removed from the other "R" terminal and the + ve terminal.
3 | If both horns and relays operate normally, the fault is in the HC 3 control unit. Replace unit.
4 | If either horn does not sound, chack further by earthing leads connocted to "C1" in the relay. If horn now operates satistactorily, the fault is in the relay. Replace unit.
Other faults, i.e.: continuously sounding horns, incorrect cycle of operation, etc., can be attributed to a faulty control unit, which should be replaced.
Retuning the 9H Alternating Horns
After horns have been in use for a long period there will probably be a deterioration in performance due to normal wear of the contact breaker mechanism. If the rest of the system is in order, proceed to reset the horn contacts as follows:
Contact Adjustment on Motorcycle
1 | Connect a voltmeter across the terminals of the horn, to check the voltage as the adjustment is being made.
2 | Connect an ammeter (range 0-25A) between terminals "C1" and "C2" of the relay which supplies the horn to be tuned.

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