Position Lamp Not Working: MOT Fail Meaning and Fix

“Position lamp not working” on an MOT means one of your sidelights or tail lights is out. Nearside is the left (passenger) side and offside is the right (driver) side, so “nearside front position lamp not working” means the front left sidelight. It is a major defect and an MOT fail, but it is usually just a blown W5W (501) bulb and a 10-minute fix.

This guide explains exactly what the MOT wording means, how to find and change the bulb, what to check when a new bulb does not cure it, the rules on LED replacement bulbs, and how to get the free retest.

What “Position Lamp Not Working” Means

A position lamp is the official name for a sidelight (front, white) or tail light (rear, red). The MOT tester records which one has failed using 3 pieces of information: front or rear, nearside or offside, and the defect.

MOT wording	Which lamp on a UK car	Usual bulb
Nearside front position lamp not working	Front left sidelight, passenger side	W5W (501)
Offside front position lamp not working	Front right sidelight, driver side	W5W (501)
Nearside rear position lamp not working	Rear left tail light	P21/5W (380), R5W (207) or W5W
Offside rear position lamp not working	Rear right tail light	P21/5W (380), R5W (207) or W5W

Nearside and offside are always judged from the driver’s seat facing forwards. Nearside is the side nearest the kerb in the UK (left); offside is nearest the centre of the road (right). They do not change on a left-hand-drive car.

The MOT result names the lamp and the defect, followed by the MOT manual reference (section 4.2.1 for a position lamp that is missing or not working). For background on the lamps themselves, see our guide to position lamps.

Is a Position Lamp Not Working an MOT Fail

Yes. The DVSA MOT inspection manual (section 4.2.1) says vehicles must have 2 front and 2 rear position lamps, and lists a position lamp that is missing or inoperative as a major defect. A major defect is a fail.

Position lamp defect	Category
Lamp missing or inoperative	Major (fail)
LED lamp with more than half its light sources out	Major (fail)
LED lamp with up to half its light sources out	Minor (pass, recorded)
Defective lens	Major (fail)
Rear position lamps can be switched off with headlamps on	Major (fail)
Colour, position or intensity not as required	Minor
Red light to the front or white light to the rear	Major (fail)

A position lamp fault is not usually dangerous, so if your old MOT certificate is still valid you can normally drive the car to be repaired. If the MOT has expired, you can only drive it to a pre-booked MOT or to a garage for pre-arranged repairs.

Front Position Lamp Not Working: Change the Bulb

On most cars the front position lamp uses a W5W (501) capless wedge bulb, fitted in a small holder in the back of the headlamp unit. A few use an R5W (207) bayonet bulb or an H6W (434) offset-pin bulb. Check the handbook or pull the old bulb to be sure.

1. Confirm which lamp: switch the sidelights on and walk round the car. Front left is nearside, front right is offside.
2. Open the bonnet: find the back of the headlamp on that side. The sidelight holder is the small one, often beside the larger headlamp bulb cover. On some cars you reach it through the wheel arch liner or need to remove the air box or battery on one side.
3. Remove the holder: most twist a quarter turn anticlockwise and pull out. Some just pull out.
4. Remove the bulb: a W5W pulls straight out of the holder. Do not twist it.
5. Fit the new bulb: push the new W5W straight in. Wear gloves or use a cloth if the glass is hot or sharp-edged.
6. Test before refitting: switch the sidelights on with the holder hanging loose to check it works, then refit and check again.

Our guide to W5W 501 bulbs has more on the base and codes, and you can order replacements from our standard miniature bulbs range. It is worth changing both sides at once, because the other bulb is the same age.

Rear Position Lamp Not Working

The rear position lamp is the tail light. Many cars use a P21/5W (380) twin-filament bulb that does both tail and brake, so check both functions:

• Tail light out but brake light works: the 5W filament has broken. Replace the P21/5W.
• Tail light and brake light both out on that side: the bulb has failed completely, or the holder or earth is faulty.
• Tail light glows brightly or brake light is dim: a bulb forced in the wrong way round in a worn holder, or a poor earth letting current find another path.

Rear bulbs are reached from inside the boot, behind a trim panel or cover, or by unbolting the rear cluster (usually 2 or 3 nuts or screws). The P21/5W has offset pins so it only fits one way. See our P21/5W 380 bulbs guide for how to tell it from a single-filament bulb.

Some cars use LED rear lamps with no replaceable bulb. If an LED tail light is out, the lamp unit (or its LED board) usually needs replacing, and the MOT treats up to half of the LEDs out as a minor defect and more than half out as a major.

New Bulb and Still Not Working

If a new bulb does not cure it, work through these checks in order.

1. Holder Corrosion

Green or white corrosion on the contacts is common where water has got into the headlamp or cluster. Clean the contacts with fine abrasive paper or a small brush and contact cleaner, bend them gently so they press firmly on the bulb, and add a smear of dielectric grease. If the holder is melted or the contacts have rotted away, replace the holder.

2. Fuse

Many cars fuse the sidelights by side (left side lamps on one fuse, right side on another) or all together. If both front and rear on one side are out, or all of them, the fuse is the first thing to check. The fuse box lid or handbook shows which one. Replace it with the same rating; if it blows again, there is a short circuit to find. Spares are in our fuses and fuse holders.

3. Earth

Use a test lamp or multimeter across the 2 holder contacts with the sidelights on. If there is 12V from the feed to bare metal but not across the holder, the earth is bad. Trace the earth wire (usually black or brown) to its bolt on the body and clean it to bare metal.

4. Wiring and Plugs

Check the plug at the back of the headlamp or cluster for corrosion and broken pins. Rear lamp wiring often breaks in the flexible gaiter between the body and the tailgate. On tractors and trailers, look for chafed looms on the chassis, rodent damage and corroded trailer plugs.

5. Light Switch or Body Control Module

On modern cars the sidelights are often switched through a body control module, and some monitor each bulb. If no lamps work and the fuses are good, a light switch or module fault is possible, and a diagnostic scan is the next step.

LED Sidelight Bulbs and CANbus Warnings

LED W5W bulbs are a popular swap, but they come with 2 catches.

CANbus Bulb Warnings

Many modern cars check the current each bulb draws. An LED bulb draws so little that the car decides the bulb has blown, shows a warning, or pulses the power so the LED flickers. A CANbus-compatible LED bulb has built-in electronics to avoid this. Some cars can be recoded to accept LEDs. If the warning still appears, refit a standard filament bulb.

Are LED Sidelight Bulbs Legal

Strictly, most LED replacement bulbs are not legal in a lamp that was type approved for a filament bulb, because the lamp is no longer in its approved form. Lamps are approved with a specific light source, and most retrofit LED bulbs are not approved as a substitute. A small number of LED substitute (LEDr) bulbs have been approved for specific uses under UN Regulation 37, and they are marked accordingly, but most marketplace LED bulbs are sold “for off-road use”.

At the MOT, the rules for sidelights are less strict than for headlamps. The manual has a “light source and lamp not compatible” defect for headlamps converted to LED or HID, but section 4.2 (position lamps) has no equivalent. A tester will look at whether the lamp works, its colour and its intensity. A front sidelight may be white or white with a slight blue tinge; a strongly blue LED, or one so dim or so bright it is clearly wrong, can be recorded as a defect. The safest choice for the MOT is a standard W5W filament bulb.

Cost and Getting the Retest

A position lamp fail is one of the cheapest MOT fails to fix. A W5W or P21/5W bulb costs a few pounds, and most people can fit one at the roadside. Some cars need more work to reach the front sidelight (removing a wheel arch liner, battery or headlamp), which is why garages charge more than the bulb on those models.

For the retest:

• Return to the same test centre by the end of the next working day after the test, and lamps (other than headlamp aim) can be rechecked as a free partial retest.
• If you leave the car at the test centre for the repair, a partial retest within 10 working days is also available.
• If you take the car away and bring it back to the same centre within 10 working days, a partial retest is available, which may be charged.
• After that, the car needs a full MOT test at the full fee.

Fix it before the test if you can: walk round with the sidelights, dipped beam and hazards on the week before your MOT. Replacement position lamps for trailers, tractors and older vehicles are in our position lamps range.

Frequently asked questions

What does nearside front position lamp not working mean?

Your front left sidelight (the passenger side on a UK car) is not working. It is usually a blown W5W (501) bulb in the back of the left headlamp.

What does offside front position lamp not working mean?

Your front right sidelight (the driver side on a UK car) is not working. Check the W5W bulb in the back of the right headlamp, then the holder and fuse.

Is a rear position lamp not working an MOT fail?

Yes. A missing or inoperative rear position lamp (tail light) is a major defect. On LED lamps, more than half the LEDs out is also a major defect.

Will an LED sidelight bulb pass the MOT?

Often, if it works, is white (not strongly blue) and is not obviously too dim or bright. Most LED retrofit bulbs are not type approved, though, and they can cause bulb warnings on CANbus cars. A standard W5W is the safest option.

Can I drive with a position lamp not working?

If your current MOT is valid, you can drive to get it fixed, but it is an offence to use the car at night without working position lamps. Replace the bulb before driving in the dark.