Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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Tests for voltage at the battery positive voltage terminal of the horn relay coil.
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Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.
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The horns need maximum current flow to operate properly. A high resistance (greater than 0.5ohms) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.
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The horn relay control circuit includes the horn slip ring and the horn switch. The slip ring and the switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you review the system operation and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms - Horns |
2 | Depress the horn switch. Do the horns operate? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 11 | |
4 |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 12 |
Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 13 | |
6 | Momentarily connect a 15 amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Do the horns operate? | -- | Go to Step 9 | Go to Step 7 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 14 |
8 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 15 |
9 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
Repair the high resistance in the horn control circuit or the horn ground circuit. (A resistance as low as 0.5ohms could cause operating problems with the horns. Also, though unlikely, it is possible that both horns are defective.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- | |
11 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- |
Repair the open or short to voltage in the horn relay control circuit. (The horn relay control circuit includes the horn slip ring and the horn switch). Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- | |
13 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- |
14 | Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- |
15 | Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 17 | -- |
16 | Replace the horn relay. Did you complete the replacement? | -- | Go to Step 17 | -- |
17 | Operate the horns. Do the horns operate properly? | -- | System OK | Go to Step 1 |
