Instructions for fitting and maintenance of Lucas “Altette” horns

MODELS HF 1234 AND HF 1235


To obtain the best results from the horn some consideration must be given to its mounting, and great care must be taken to ensure that it is securely clamped to some substantial member of the vehicle. Details of design vary so considerably that it is impossible to recommend one particular part on which the horn can be mounted.

HF1234 horns are designed for external mounting, whilst HF1235 horns are designed for under-bonnet mounting.

In whatever position the horn is mounted, care must be taken to clamp it firmly and to ensure that there is no possibility of it fouling the engine or fittings through vibration when on the road.


Before making any alterations to the wiring, disconnect the battery lead, or if a battery master switch is fitted, switch to the off position to avoid the possibility of short circuits. On vehicles fitted with Lucas combined cut-out and voltage regulator units, a convenient battery supply point is terminal A2 on the control box or fuse unit.

All leads should be kept as short as possible and securely clamped in position. Do not clamp cables against sharp edges where there is a danger of abrasion through vibration. Avoid taking cables round acute bends or where that can be splashed by oil or water.

The cable to be used must be of adequate size to carry the horn current, which is 4 amps for 12 volt horns and 6 amps for 6 volt horns.

Prepare a length of cable of adequate current carrying capacity to connect between the battery supply point and one of the horn terminals. The other terminal on the horn should be connected to one terminal of the horn-push. Normally the horn-push on the vehicle will already have cables connected to it and the lead from the horn should be joined to one of these at a suitable point. If the horn-push is not earthed internally, the other terminal on the push must be connected to a good earthing point on the vehicle chassis.


Before being passed out of the Works, the horn is adjusted to give its best performance, and will give a long period of service without any alteration. If the horn fails, or becomes uncertain in its action, first ascertain that the trouble is not due to some outside source, e.g. a loose connection or short circuit in the wiring of the horn. Ensure that the horn terminals are fully tightened. It is also possible that the performance of the horn may be impaired by the fixing bolts working loose.

If, after carrying out the above examination, the trouble is not rectified, the horn may need adjustment, but this should not be necessary until the hons have been in service for a long period. Adjustment does not alter the pitch of the note; it merely takes up wear of moving parts.


Correct adjustment of the horn requires the use of a D.C. ammeter (0-10 amps. scale) in series with the horn under test.

The correct current consumption should be:

6 volt model    …        6 amps

12 volt model  …        4 amps

To adjust, operate the horn push and turn the contact breaker adjustment screw (Fig.1) in an anticlockwise direction until the horn just ceases to sound. Then turn the serrated adjustment screw clockwise six notches (a quarter of a turn) and check the performance and current consumption. Further adjustment should be made by turning the adjustment screw one ‘notch’ at a time in a clockwise direction and re-checking, until the best performance is obtained with current consumption not exceeding the values quoted.

Fig. 1. Rear view of horn.

If a suitable ammeter is not available, the following procedure can be adopted if the horn note is considered to have deteriorated: –

Operate the horn push and turn the adjustment screw anticlockwise until the horn just ceases to sound. Release the horn-push and turn the adjustment screw clockwise for six ‘notches’, when the original performance should be restored.

Finally, if the note is still unsatisfactory, do not dismantle the horn, but return it to a Lucas Service Depot or Agent for examination.


Editor’s note: The Lucas Altette model HF 1234 was fitted to the TC, certainly the later TC, as it quotes this model number in my copy of ‘Lucas Equipment’ for the 1949 TC.

I’m not sure of the source of these instructions, but I have re-typed them because the print size in the original document was rather small.

Russell Dade contributed a fine article entitled Altette Soundings which covered the restoration of an Altette model HF1234 in Issue 56 (October 2019) of TTT 2.

Here’s his finished example:

Any mention of horns and some of us immediately think of ‘Taff the Horn’ (Taff Isaac down in South Wales). I’m not sure if Taff is still around (I hope he is) but there is a message on his website  that “TAFFS PARTS NOW BEING TAKEN OVER BY terrybinns1957(at)”.

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