1. Check the Bulbs:
* Access: This is the easiest check. Locate the cab lights (usually near the bed). Remove the lens covers to access the bulbs.
* Inspection: Visually inspect the bulbs for filament breakage. If they look burnt out, replace them with new bulbs of the correct type and wattage (check your owner's manual or the old bulb for specifications).
* Test (optional): If you have a multimeter, test the bulbs for continuity (a good bulb will show a low resistance reading).
2. Check the Fuses:
* Locate the Fuse Box: Your 1999 Ford Ranger will have an under-hood fuse box and possibly one inside the cab (usually under the dash). Consult your owner's manual for the location and a fuse diagram.
* Identify the Cab Light Fuse(s): The diagram should specify the fuse(s) responsible for the cab lights. Look for a blown fuse (a broken filament inside the fuse). If found, replace it with a fuse of the same amperage rating.
* Test (optional): If you have a multimeter, you can test the fuse for continuity to confirm it's blown.
3. Check the Wiring:
* Wiring Harness: Inspect the wiring harness leading to the cab lights for any visible damage (cuts, fraying, corrosion). Look particularly at the connections where the wires meet the bulbs and the main harness.
* Connections: Carefully check all connections for corrosion or loose wires. Clean any corroded connections with a wire brush and electrical contact cleaner. Ensure all connections are securely fastened.
* Continuity Test (Advanced): If you have a multimeter, you can test the continuity of the wiring from the fuse to the lights. This requires disconnecting the wires at various points to isolate the problem area.
4. Check the Switch (If Applicable):
* Location: Some cab lights may have an individual switch inside the cab. If yours does, ensure it's turned on.
* Testing: Check if the switch is functioning correctly. If you have a multimeter, you can test the switch for continuity in the on and off positions.
5. Grounding Issues:
* Ground Connection: Cab lights require a good ground connection to work. Inspect the ground wire(s) connecting the lights to the vehicle's chassis. Clean any corrosion and ensure a secure connection.
Important Considerations:
* Owner's Manual: Always consult your owner's manual for specific diagrams and fuse information for your vehicle.
* Safety: Always disconnect the negative battery terminal before working on electrical systems.
* Professional Help: If you're not comfortable working with electrical systems, it's best to take your vehicle to a qualified mechanic.
By systematically checking these items, you should be able to pinpoint the reason your cab lights aren't working. Remember to replace any blown fuses with the correct amperage rating and use the correct type and wattage bulbs.
