H1, H3 and H11 Bulbs Explained: Bases, Wattages and Where They Fit on Tractors
H1, H3 and H11 are single-filament halogen bulbs, 55W at 12V and 70W at 24V, with different bases. Which fits work lamps, beacons, spots and headlamps.
In this guide
H1, H3 and H11 are all single-filament halogen bulbs, rated 55 watts at 12 volts and 70 watts at 24 volts, but each has a different base, so they do not swap. The H1 (UK number 448) has a P14.5s base with a single spade terminal and is used in work lamps, spot and driving lamps and halogen rotating beacons. The H3 (UK 453) is a short bulb on a PK22s base with a flying lead, used mainly in work lamps and fog lamps. The H11 (UK 711) has an L-shaped PGJ19-2 plastic base with a built-in plug, and is used in more modern headlamps, fog lamps and work lamps.
This guide explains how to tell the three apart, what each is used for on tractors and farm machinery, how to choose between 12V and 24V, and where LED versions stand on the road.
H1, H3 and H11 compared
| H1 | H3 | H11 | |
|---|---|---|---|
| UK number | 448 | 453 | 711 |
| Base | P14.5s | PK22s | PGJ19-2 |
| Connection | One spade terminal on the end | Short flying lead with a spade connector | Plastic base with a 2-pin socket |
| Filaments | One | One, lying across the bulb | One |
| 12V rating | 55W | 55W | 55W |
| 24V rating | 70W | 70W | 70W |
| Typical output (12V 55W) | About 1,550 lumens | About 1,450 lumens | About 1,350 lumens |
| Common uses | Work lamps, spot and driving lamps, rotating beacons, some main beams | Work lamps, fog lamps, spot lamps | Dipped beam headlamps, fog lamps, newer work lamps |
Output figures are the standard rated values for a normal halogen bulb. Brighter “plus” bulbs give more light for a shorter life, and long-life bulbs the other way round. Our guide to halogen bulb lifespan explains the trade-off.
H1 bulbs
The H1 is the oldest of the three and still one of the most common bulbs in halogen work lamps on tractors, loaders and combines. It is a straight bulb on a round metal flange with locating tabs, and the single spade terminal sticks out of the end; the lamp body provides the earth, or a separate earth lead is fitted. Most halogen rotating beacons use an H1, so it is also the bulb to carry in the cab for a beacon. H1 bulbs are also used in many round spot and driving lamps.
A 24V H1 for 24 volt machines is rated 70W. Because the base is the same, it is easy to fit the wrong voltage by mistake; see 12V or 24V below.
H3 bulbs
The H3 is a short bulb with the filament lying across it, on a small round PK22s base, with a short wire lead and a spade connector coming out of the side. The lead plugs onto a terminal inside the lamp. It is the standard bulb in many older square and round halogen work lamps and in fog lamps, because it is compact enough for small lamp bodies. On tractors it is common in cab roof and mudguard work lamps; for example, it is used in work lamps on John Deere 5M, 6010, 6M and 6R series tractors, and we stock that H3 bulb.
When you fit an H3, make sure the lead is not trapped by the retaining clip and the spade is pushed fully home, as a loose spade terminal is a common cause of a flickering work lamp.
H11 bulbs
The H11 is the newest of the three. The bulb sits in an L-shaped plastic base with a sealed 2-pin socket, so it twists into the back of the lamp and the wiring plug clips on. It is used for dipped beam in many headlamps built from the mid 2000s, and in fog lamps and some work lamps. On tractors it is found on models such as the John Deere 6030 and 7030 series, where we stock a long-life H11 bulb.
The H11 looks like the H8, H9 and H16, which share the same style of base with different keying and wattages. They are not interchangeable: an H9 is 65W and runs hotter, and fitting one in a lamp built for H11 can damage the lamp and wiring. Always match the code printed on the old bulb.
12V or 24V
All three come in 12V (55W) and 24V (70W) versions, with the same bases. A 12V bulb fitted to a 24V machine will blow within seconds, and a 24V bulb on a 12V machine gives only a weak, orange light. Check the voltage on the old bulb’s base or glass, or in the operator’s manual. Most tractors are 12V, while many telehandlers, diggers, lorries and some larger tractors are 24V. Our guide to 12V and 24V tractor systems explains how to tell. Shop 12V bulbs or 24V bulbs.
Can I fit LED H1, H3 or H11 bulbs?
In a work lamp used off the road, an LED replacement bulb is your choice, but it is rarely a good one. A halogen work lamp’s reflector is designed around the exact position of a filament, so an LED bulb usually gives a patchy beam, and cheap LED bulbs can interfere with GPS and radio. A complete LED work lamp is brighter, sealed and lasts far longer.
In a headlamp or fog lamp used on the road, an LED bulb in a halogen lamp is only legal where the LED replacement is approved for that lamp. For vehicles that have an MOT, such a bulb must carry the manufacturer’s approval sticker; without it, it is a fail. Most LED H1, H3 and H11 bulbs sold online are marked for off-road use only. See which lights fail an MOT and LED headlamp conversions.
How to change an H1, H3 or H11 bulb
- Switch the lamp off and let it cool: a halogen bulb runs hot enough to burn.
- Remove the back cover or the rear of the lamp, or on some work lamps the front lens and rim.
- H1 and H3: pull off the spade connector, release the spring clip and lift the bulb out. H11: unclip the wiring plug, then twist the bulb a quarter turn anticlockwise and pull it out.
- Fit the new bulb holding it by the base, not the glass. Grease from fingers shortens a halogen bulb’s life; if you touch the glass, wipe it with methylated spirit.
- Seat the base fully, refit the clip or twist it home, reconnect and test before refitting the cover.
- Check the cover seal. Water getting into the lamp is the main reason these bulbs fail early.
If the same bulb keeps failing, see why tractor bulbs keep blowing.
Frequently asked questions
What is the difference between H1 and H3 bulbs?
Both are 55W single-filament halogen bulbs at 12V, but the H1 is a straight bulb on a P14.5s base with a spade terminal on the end, while the H3 is a shorter bulb on a PK22s base with a flying lead. They are not interchangeable.
Is an H11 the same as an H8 or H9?
No. They look alike and share a similar base style, but the keying and wattage differ. Fit the bulb code shown on the old bulb or in the lamp.
What does a halogen rotating beacon use?
Most halogen rotating beacons use an H1 bulb, in 12V or 24V to suit the machine. Check the old bulb before ordering, as a few use an H3.
What is the UK number for an H3 bulb?
The H3 is the 453. The H1 is the 448 and the H11 is the 711.
Are 24V H3 bulbs the same as 12V?
They have the same base but a different filament, rated 70W for 24V. Fitting a 12V bulb in a 24V lamp will blow it straight away.