HOSE,FUEL 1040370 - Caterpillar

Table 1
Horn Frequency (Hz) Loudness at 2 Meters (db (A))
High Tone 425 20 112 4
Low Tone 340 20 112 4 Probable Causes:
The fuse for the horns is blown.
The connectors for the horns are damaged.
The relay for the horns is bad.
The horn button is bad.
The horn or horns are bad.
Table 2
Coil Unenergized Coil Energized
Wire Resistance Resistance
Wire R14-30-BK(Black) to Wire R14-87A-BK(Black) Less than 0.5 Ohms Open
Wire R14-30-BK(Black) to Wire R15-87-BK(Black) Open Less than 0.5 Ohms
Table 3
Machine Horn Does Not Respond to Operator Console
Troubleshooting Test Steps Values Results
Test Step 1. Check the Fuse.
A. Check the "Horn/10A Converter" fuse in the cab fuse block panel to see if the fuse is blown.
The fuse is not blown. OK – The fuse is not blown.
Proceed to Test Step 2.
Not OK – The fuse is blown.
Repair: Replace the fuse and check the operation of the horn. If the fuse blows again, use the electrical schematic and check for shorts to ground in the horn power circuits.
STOP.
Test Step 2. Check the Connectors for Damage.
A. Using the electrical schematic, visually inspect the horn circuits connectors for damage.
The connectors are not damaged. OK - The connectors are not damaged.
Proceed to Test Step 3
Not OK – The connectors have failed.
Repair: Repair or replace the damaged connector or connectors. Check for proper operation.
STOP.
Test Step 3. Visually Inspect the Horn Relay.
A. Locate the horn relay in the cab relay/fuse block. Remove the relay and visually inspect the relay for damage.
The relay is not damaged. OK – The relay is not damaged.
Proceed to Test Step 4.
Not OK – The relay appears damaged.
Repair: Install a new relay and check operation.
STOP.
Test Step 4. Check the Horn Relay Coil Resistance.
Using a multimeter, check the resistance of the relay coil.
The relay coil resistance is between 76 and 112 Ohms. OK – The relay coil resistance is between 76 and 112 Ohms.
Proceed to Test Step 5.
Not OK – The relay coil resistance is not between 76 and 112 Ohms.
Repair: Replace the relay and check operation.
STOP.
Test Step 5. Check the Horn Relay Contacts.
Check the position of the relay contacts with the relay coil unenergized and energized.
The contacts meet the specifications in Table 2 OK – The contacts meet the specifications in Table 2.
Proceed to Test Step 6.
Not OK – The contacts do not meet the specifications in Table 2.
Repair: Install a new relay and check operation.
STOP.
Test Step 7. Check for Voltage at the Horn Harness Connectors.
A. Remove the connectors from the horns. Actuate the horn switch and check each connector for voltage. The voltage should be approximately 24 VDC.
The voltage measured at each horn connector is approximately 24 VDC. OK – The voltage measured at each horn connector is approximately 24 VDC.
Proceed to Test Step 8.
Not OK – The voltage measured at one or both horn connectors is not approximately 24 VDC.
Repair: Using the system electrical schematic, check the horn circuit or circuits for opens. Repair or replace the harness and check the operation of the horn.
STOP.
Test Step 8. The Horn is Bad.
A. Determine