Here you can get how to Fixing a reversing light, Blown bulb, Fuses, Wiring check, Switch test and Adjusting the switch on gearbox.
Reversing lights are not generally a legal requirement but they’re useful. They serve two purposes – to warn other road-users you’re close to reverse, and to provide light if you’re reversing within the dark.
The circuit may be a simple one, consisting of one or two rear light units operated by a switch, so if anything goes wrong it’s easy to see. On most cars the switch is mounted on the gear box and it’s operated automatically when reverse gear is chosen. If the lights were added after the car was made, the switch could also be a manually operated one mounted on the dash.
One of the most common problems may be a blown bulb. to test it, remove it from its holder and connect it across the battery terminals with a brief extension wire. If the bulb lights up the fault lies elsewhere within the circuit.
First make sure the bulb holder and wiring terminals are clean and bright. If there’s any corrosion, clean it up with wet-or-dry paper then refit the bulb and retest. If the bulb still fails to light, the fuse may have blown. you ought to also suspect a blown fuse if two reversing lights go together.
In many cases the fuse protecting the reversing lights also covers other accessories (see your car handbook to find out which ones). If none of those is working, renew the fuse and test again. If the fuse blows as soon as you test it there’s a brief circuit somewhere – it’s going to be easier to get an auto-electrician to trace it.
If other components protected by the fuse are still working, then you would like to see the rest of the circuit using a test lamp.
Turn the ignition on and remove the feed wire to the coil to stop it overheating. Select reverse gear or the ‘R’ position on an automatic. Clip the test lamp to a good earth point and probe the live terminal within the bulb holder. If the test lamp lights, current is reaching the bulb. If the bulb has a separate earth lead, the fault must dwell that.
To check the world run a brief wire from the bulb holder earth to a point on the car body. Refit the bulb and check again. If the bulb works, renew the world lead.
If no current was reaching the bulb-holder you’ll have to check back along the rest of the circuit. Find from your workshop manual the color and route of the reversing wires. Carefully probe the wire along its length. In most cases the wire will disappear into the most loom where you cannot get at it. If you find the fault is inside the loom you’ll bypass it by splicing during a new wire.
If there’s no current within the wiring, check the gearbox switch. On a manual car there’ll be two switch terminals. On an automatic there’ll be four, two of which are for the inhibitor circuit and will not be disturbed (unless you’re adjusting the switch – see sideline, left). Check your manual to seek out the right terminals for testing.
It may be easier to raise the car on axle stands. Then turn the ignition on and choose reverse gear. Connect the test lamp to earth and probe one terminal, then the other. If the lamp lights on both terminals, the fault is within the wiring between the switch and reversing lights. If the lamp fails to light in the least , check the wiring between the fuse and switch. If the lamp only lights on one terminal, the switch is either broken or needs adjusting. To replace a reversing light switch, disconnect the wiring and either unscrew the switch or, if a lock nut is used, release this. Replace the switch in reverse order, then adjust it.
Adjusting the switch on a manual gearbox
To adjust the lock nut type switch, connect a circuit tester across the terminals.
Select reverse gear and slacken the lock nut (right). Screw within the switch until the tester just lights, then do up the lock nut. Other switches are adjusted by unscrewing the switch completely and adding or subtracting shims (right). The setting is correct when the tester just illuminates because the switch is fully tightened.
Adjusting the switch on an automatic gearbox
Some automatic gearbox switches are adjustable. the basic method for adjusting is described here, but you ought to always ask your workshop manual for the exact procedure. Start by identifying the four switch wires and terminals, then disconnect them. Move the gear lever to the drive position. Slacken the locknut and unscrew the switch from the gearbox a couple of turns. Using a circuit tester with its own power supply (not a test lamp), connect it across the two reversing light terminals. Slowly screw the switch in until the light goes out. Mark the switch and gearbox with a dab of paint.
Now connect the circuit tester across the two inhibitor terminals. Screw the switch in further until the tester lights up again, and mark this position on the gearbox in line with the previous mark you made on the switch. Screw the switch out until its mark is strictly halfway between the two marks on the gearbox (below), then tighten the locknut.