Jeep 1997 Grand Cherokee Service Manual page 493

ZG
DIAGNOSIS AND TESTING (Continued)
FOG LAMP DIAGNOSIS
CONDITION
FOG LAMPS ARE DIM
WITH ENGINE IDLING
OR IGNITION TURNED
OFF.
FOG LAMP BULBS BURN
OUT FREQUENTLY.
FOG LAMPS ARE DIM
WITH ENGINE RUNNING
ABOVE IDLE.
FOG LAMPS FLASH
RANDOMLY.
FOG LAMPS DO NOT
ILLUMINATE.
POSSIBLE CAUSES
1. Loose or corroded
battery cables.
2. Loose or worn
generator drive belt.
3. Charging system output
too low.
4. Battery has insufficient
charge.
5. Battery is sulfated or
shorted.
6. Poor lighting circuit
Z1-ground.
7. Both fog lamp bulbs
defective.
1. Charging system output
too high.
2. Loose or corroded
terminals or splices in
circuit.
1. Charging system output
too low.
2. Poor fog lamp circuit
ground.
3. High resistance in fog
lamp circuit.
4. Both fog lamp bulbs
defective.
1. Poor fog lamp circuit
ground.
2. High resistance in fog
lamp circuit.
3. Faulty fog lamp switch
circuit breaker.
4. Loose or corroded
terminals or splices in
circuit.
1. Blown fuse for fog
lamps.
2. No ground at fog
lamps.
3. Faulty fog lamp switch.
4. Broken connector
terminal or wire splice in
fog lamp circuit.
CORRECTION
1. Clean and secure battery cable clamps and posts.
2. Adjust or replace generator drive belt.
3. Test and repair charging system, refer to Group 8A.
4. Test battery state-of-charge, refer to Group 8A.
5. Load test battery, refer to Group 8A.
6. Test for voltage drop across Z1-ground locations,
refer to Group 8W.
7. Replace both lamp bulbs.
1. Test and repair charging system, refer to Group 8A.
2. Inspect and repair all connectors and splices, refer to
Group 8W.
1. Test and repair charging system, refer to Group 8A.
2. Test voltage drop across Z-1 ground, refer to Group
8W.
3. Test amperage draw of fog lamp circuit.
4. Replace both fog lamp bulbs.
1. Repair circuit ground, refer to Group 8W.
2. Test amperage draw of fog lamp circuit.
3. Replace fog lamp switch.
4. Repair connector terminals or splices, refer to Group
8W.
1. Replace fuse, refer to Group 8W.
2. Repair circuit ground, refer to Group 8W.
3. Replace fog lamp switch.
4. Repair connector terminal or wire splices.
LAMPS 8L - 3