Vehicle bulb guides: types, bases and how to replace them
Bulb guides explain the halogen and filament bulbs fitted to tractor and trailer lamps: what each code such as H4, H7, H3, P21W, W5W or R5W means, which base it has, which lamp it goes in and how to replace it. The section holds eight guides, with one guide per common bulb type and general guides on lifespan and 12V against 24V.
8 guides
- Bulbs
880 and 881 Bulbs Explained: The H27W Fog and Spot Bulb, Its Base, and How to Replace It
An 880 bulb is a 27-watt single-filament capless bulb on a PG13 base, used for fog lamps, spot lamps, and daytime running...
- Bulbs
H6W Bulbs Explained: The 434 BAX9s Sidelight Bulb, Its Offset-Pin Base, and How to Replace It
An H6W bulb is a 6-watt single-filament bulb on a BAX9s offset-pin bayonet base, used for sidelights, parking lamps, and interior lamps....
- Bulbs
W16W Bulbs Explained: The 921 Capless Reversing Bulb, Its Base, and How to Replace It
A W16W bulb is a 16-watt single-filament capless bulb on a W2.1x9.5d wedge base, used for reversing lamps, high-level brake lamps, and...
- Bulbs
R5W Bulbs Explained: The 207 BA15s Sidelight Bulb, Its Base, and How to Replace It
An R5W bulb is a 5-watt single-filament bulb on a large single-contact BA15s bayonet base, used for sidelights, tail lights, number plate...
- Bulbs
Halogen Bulb Lifespan: What Affects It and How to Maximise It
A halogen bulb lasts between 500 and 1,000 hours of use in normal conditions. The figure is the rated life set by...
- Bulbs
Why Do My Tractor Bulbs Keep Blowing: Common Causes and Fixes
A tractor bulb that keeps blowing has one of five root causes: charging-system over-voltage, vibration, wiring or earth faults, fitting damage (skin...
- Bulbs
H4 vs H7 Bulbs: Differences, Uses, and Which One You Need
H4 and H7 bulbs are the two most common halogen headlamp bulbs fitted to tractors, telehandlers, and farm vehicles in the UK....
- Bulbs
Vehicle Bulb Types Explained: A Complete Reference by Code
A vehicle bulb is identified by an alphanumeric code that fixes its base shape, filament arrangement, wattage and rated voltage. The four...
Reading a bulb code
A bulb code names the filament type and the base. H-series bulbs (H1, H3, H4, H7) are halogen headlamp and work light bulbs with a push-fit or three-pin base. P21W and P21/5W are bayonet BA15s and BAY15d bulbs for brake, tail and indicator lamps. W5W and W16W are capless wedge bulbs for side, plate and reversing lamps. R5W and T4W are small bayonet bulbs for markers. Each guide gives the wattage, the base, the lamps it fits and the LED alternative where one exists.
Voltage and lifespan
A bulb must match the vehicle voltage: a 12V bulb on a 24V system fails within seconds. Halogen bulbs last 300 to 1,000 hours depending on vibration and voltage spikes, and the lifespan guide explains why bulbs keep blowing on a particular lamp. Replacement bulbs for every code are in stock, including assortment boxes for the workshop.