Section 13-06: Horn
| 1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual
|
DIAGNOSIS AND TESTING
Pinpoint Tests
NOTE: Use Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to perform electrical pinpoint tests.
PINPOINT TEST A: HORN SOUNDS CONTINUOUSLY
A1 CHECK HORN SWITCH CIRCUIT FOR SHORT
- Remove relay.
- Disconnect positive battery cable and wait one minute.
- Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent connected to a known good ground, connect other lead to Circuit 1 (DB) at relay connector.
Is resistance 5 ohms or less?
| Yes | No |
|---|
| GO to A2. | REPLACE shorted horn relay. RESTORE vehicle. RETEST system. |
A2 CHECK HORN SWITCH FOR SHORT
- Disconnect horn switches. Refer to Horn Switch in the Removal and Installation portion of this section.
- With ohmmeter still connected to relay connector and ground read resistance.
Is resistance 5 ohms or less?
| Yes | No |
|---|
| GO to A3. | REPLACE shorted horn switch. RESTORE vehicle. RETEST system. |
A3 CHECK FOR SHORTED AIR BAG SLIDING CONTACT
- Disconnect ohmmeter from relay connector.
- Carefully check resistance of each contact.
Is resistance 5 ohms or less?
| Yes | No |
|---|
| REPLACE sliding contact. RESTORE vehicle. RETEST system. | SERVICE short to ground Circuit 6 (Y/LG). RESTORE vehicle as outlined. RETEST system. |
PINPOINT TEST B: HORN SYSTEM INOPERATIVE
B1 PRELIMINARY CHECK
- Check fuse C in Power Distribution Box.
- Check for loose connections and wiring.
Do components check OK?
| Yes | No |
|---|
| GO to B2. | SERVICE or REPAIR as required. |
B2 CHECK HORNS
- Disconnect battery negative cable.
- Disconnect horns.
- Connect jumper wire from battery positive terminal to horn positive terminal.
- Connect jumper wire to battery negative terminal then touch other end of jumper to horn ground connection. Repeat for second horn.
Does horn sound?
| Yes | No |
|---|
| GO to B3. | REPLACE horns as required. |
B3 CHECK CIRCUIT 6 (Y/LG) FOR SHORT TO GROUND
- Check for ground short in Circuit 6 (Y/LG) between horns and horn relay.
- Check for ground short between high and low pitch horns.
Are circuits OK?
| Yes | No |
|---|
| GO to B4. | REPAIR ground short in Circuit 6 (Y/LG). |
B4 CHECK CIRCUIT 6 (Y/LG)
- Check for open in Circuit 6 (Y/LG) between horns and horn relay.
Is circuit OK?
| Yes | No |
|---|
| GO to B5. | REPAIR open in Circuit 6 (Y/LG). |
B5 CHECK CIRCUIT 38 (Y) AND 460 (Y/LB) FOR SHORT TO GROUND
- Check for ground short in Circuit 38 (Y) and 460 (Y/LB) between horn relay and fuse C, and between fuse C and battery.
Are circuits OK?
| Yes | No |
|---|
| GO to B6. | REPAIR ground short in Circuit 38 (Y) or 460 (Y/LB) as required. |
B6 CHECK CIRCUIT 38 (Y) AND 460 (Y/LB)
- Check for open in Circuit 38 (Y) and 460 (Y/LB) between horn relay and fuse C, and between fuse C and battery.
Are circuits OK?
| Yes | No |
|---|
| REPLACE horn switch. | REPAIR open in Circuit 38 (Y) or 460 (Y/LB) as required. |