| 0 | PRELIMINARY CHECKS | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Check, by operating the horn control on the steering wheel, that the travel is correct | Move on to Step 1 | Travel not correct | Remove the steering wheel and check that there are no impediments to the travel. Op. 4110A10 STEERING WHEEL - R+R FOR REPLACEMENT OR CHECKSIf there are problems, replace the faulty component |
| 1 | CHECK ON INTERVENTION OF FUSE | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Check that the horn protective fuse has not blown.It can be found in the engine compartment junction unit and is the third fuse in the first row F10 (15 A). | Move on to Step 2 | The fuse has blown | Replace the fuse and search for the cause of the problem. |
| 2 | RELAY CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Swap the horn relay feed T3 (it is the middle one in the top row) with the one for the main beam headlamps T2 (it is the first on the left in the top row) and check that the horn is working properly. | Move on to Step 3 | The horn continues not to work | Restore the relays to their places and move on to Step 4 |
| 3 | RELAY CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Check that the main beam headlamps are working. If the result is positive, remove the horn relay feed and check that the contacts do not show signs of oxidation or deformation. | End of diagnosis | 1. The high beams do not work | 1. Replace the main beam headlamp relay (which was originally the one for the horns) |
| 2. There are irregularities at the engine compartment junction unit contacts. | 2. Renew the contacts.If necessary, replace the engine compartment junction unit Op. 5505A13 ADDITIONAL JUNCTION UNIT IN ENGINE COMPARTMENT - R.R. |
| 4 | RELAY ELECTRICAL CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Undo the fastenings for the engine compartment junction unit and check, using a tester, that the power supply and the earth for the horn relay feed are correct. Op. 5505A13 ADDITIONAL JUNCTION UNIT IN ENGINE COMPARTMENT - R.R. | Move on to Step 5 | Relay line electrical problems. | Move on to Step 8 |
| 5 | HORN ELECTRICAL CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Using a tester, connect to the horn power supply line and check that whilst the horn is working the supply voltage is more than 11.4 V.Also check the continuity and the insulation of the line | Move on to Step 6 | 1. The voltage is below 11.4 V | 1. Check the cause of the power supply and restore the correct power supply.Possibly See Test 5530BC BATTERY CHARGE CHECK |
| 2. Other electrical problems | 2. Restore the correct electrical connections See E3010 HORNS |
| 6 | CHECK POSITIONING OF HORNS | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Check that both the horn casing and the bracket are not touching or are not in the immediate vicinity (less than 10 mm) of other objects (other components, cables, pipes, etc.) | Move on to Step 7 | Horn bracket or casing interfering with other components. | Eliminate the cause of the interference |
| 7 | STEERING COLUMN SWITCH UNIT CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Remove the steering wheel and check that there is nothing preventing the operation of the horn control switch.Using a tester in parallel to the switch check that, whilst it is working, the supply voltage is more than 11.4 V | Move on to Step 9 | 1. Switch stuck open | 1. Replace the steering wheel Op. 4110A10 STEERING WHEEL - R+R FOR REPLACEMENT OR CHECKS |
| 2. Switch power supply problems. | 2. Replace the steering column switch unit. Op. 5550A10 STALK UNIT ASSEMBLY - R+R |
| 8 | HORN CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| Remove the horn and connect it directly to a battery charger. Op. 5550B30 L/H OR R/H HORN (ONE) - R+RCheck that a sound produced and that there are no unpleasant noises (knocking/buzzing) | Move on to Step 9 | Sound faulty or no sound produced. | Replace the horn Op. 5550B30 L/H OR R/H HORN (ONE) - R+R |
| 9 | ELECTRICAL CIRCUIT CHECK | ALL OK | PROBLEMS ENCOUNTERED | ACTION |
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| The problem is due to the presence of an irregular electrical absorption source in the electrical equipment.Search for and eliminate this cause | if necessary we will process suitable diagnoses for the battery, alternator and wiring. |
| End of diagnosis | | |