OVERHAULING OF HORN

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Aim:

OVERHAULING OFHORN & TUNING

TOOLS REQUIRED:

1. SCREW DRIVER (-,x)
2. FEELER GAUGE
3. MULTY METER
4. 10mm D/E OPEN SPANNER

MATERIALS REQUIRED

1. EMERY PAPER
2. COTTON WASTE
3. GREASE

PROCEDURE

Dismantling 

Disconnect the wires from the horn assembly and remove the mounting nuts and take out the horn unit

Remove the horn from the vehicle.

Loosen the cover fixing screws.

Remove the cover, packing washer, diaphragm assembly  and shim.

Remove the terminal's nuts and washer.

Remove the contact breaker assembly from the housing.

Inspection

Clean the contact breaker points with fine emery paper. If necessary, replace the points.

Check the coil for continuity and resistance by an ohmmeter for 12 volt - 0.75 -0.85 ohm and for 24 volt - 3.25 -3.5 ohms.

Replace the coil if found burnt or defective.

Check the diaphragm visually, replace if it is found damaged.

Check all the screw threads visually, and if necessary, replace the screws. Clean all the parts.

Assembling

Place the contact breaker assembly in its position. Fix the terminal, washer and nuts. Fit the shim, diaphragm, packing washer and
cover .

Turn the adjustment screw so that the contacts remain closed, when the armature is attracted to the core. Mornentarily energise the coil winding by a low voltage supply.

Measure the armature  air gap with the help of a dial gauge.

Note: The correct air gap settings are for low voltage - 0.020"/0.025" for high voltage - 0.016/0.022".

- Refitting horn to the vehicle and test

Tuning of horn

Check the tonal quality of the horn while blowing. If the tonal quality is not satisfactory, check the voltage at the horn terminals with the horn kept blowing.

The voltage should be 11 to 14V for a 12V horn and 22V to 28V for a 24V horn. Simultaneously check the current, (if necessary) drawn by the horn.

Turn the adjustment screw using a proper tool and check for its performance. Repeat the adjustment until a satisfactory performance is achieved.

In a twin-horn, do the tuning procedure first for one horn by disconnecting the other and vice versa.

Place the horn in its place, tighten the mounting bolts and nuts.

Connect the wires.

Check the horn button connection.

Press the horn button to ensure that the horn performs satisfactorily and the horn note is correct.

RESULT:

THE OVERHAULING OF ELECTRIC HONE IS DONE SUCCESSFULLY.

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