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A weak factory horn can be easy to miss in traffic, but upgrading it also means checking space, wiring capacity, and legal requirements before you install anything. The HELLA B133 SuperTone Horn Set, part 3AG 003 399-801, combines a 300 Hz low tone with a 500 Hz high tone and is rated at 118 dB(A). Its strong output and rugged 12 V design make it appealing for drivers who want a more noticeable warning signal, but the electrical load and 123 mm horn diameter mean it is not a simple fit for every vehicle. This review explains the specifications, installation demands, sound characteristics, and practical limitations so you can decide whether it suits your setup.
Quick Verdict
Rating: 8.5/10
Best For: Drivers with a 12 V vehicle who want a loud, dual-tone warning horn and have enough mounting space and electrical capacity.
Bottom Line: The B133 stands out for its 118 dB(A) output, 300/500 Hz tone pairing, and rugged HELLA construction. Its main tradeoff is installation: the pair draws significant current and the 123 mm housings need more room than many compact factory horns.
Key Takeaways
- The HELLA B133 combines a 300 Hz low tone and 500 Hz high tone to create a distinct dual-tone warning signal.
- HELLA rates the horn at 118 dB(A), making it considerably more attention-focused than many basic factory horns.
- Each horn measures about 123 mm in diameter, with a listed overall height of 135 mm, width of 125 mm, and depth of 85 mm.
- The system is designed for 12 V electrical systems. HELLA lists 66 W power consumption and a maximum current of 5.5 A per horn.
- The B133 uses flat blade-style electrical connections and requires secure wiring, adequate circuit capacity, and a solid mounting point.
- HELLA lists IP65 protection, ECE R28 approval, and an operating range from -40 °C to +60 °C.
- Part 3AG 003 399-801 should not be confused with part 3AG 003 399-821, which HELLA identifies as the B133 set supplied with a 5-pin relay.
Key Features and Specifications
| Specification | Detail |
|---|---|
| Brand | HELLA |
| Product | B133 SuperTone Horn Set |
| Part number | 3AG 003 399-801 |
| Product type | Electric dual-tone disc horn set |
| Rated voltage | 12 V |
| Low tone | 300 Hz |
| High tone | 500 Hz |
| Sound level | 118 dB(A) |
| Power consumption | 66 W per horn |
| Maximum current | 5.5 A per horn |
| Diameter | 123 mm |
| Overall height | 135 mm |
| Width | 125 mm |
| Depth | 85 mm |
| Connection | Flat blade-style connector |
| Housing | Black metal housing with red protective grille |
| Quantity | 2 horns, low tone and high tone |
| Protection | IP65 |
| Approval | ECE approved, fulfils ECE R28 |
| Temperature range | -40 °C to +60 °C |
| Specified service life | 100,000 cycles under ECE R28 testing |
What Is the HELLA B133 SuperTone Horn Set?
The B133 is a pair of electric disc horns designed to produce two frequencies at the same time. One unit provides the 300 Hz low tone and the other produces the 500 Hz high tone. Together, they create the strong, penetrating sound associated with HELLA’s SuperTone line.
HELLA positions the B133 for cars and demanding driving environments, including off-road use. The product is more substantial than a small factory horn, so its appeal is strongest when you want greater warning presence and are willing to plan the installation around its physical size and electrical requirements.
Who Should Buy It?
Best For
- Drivers who want a louder 12 V replacement or upgrade over a weak factory horn.
- Vehicles with enough front-end space for two 123 mm disc horns.
- Owners comfortable with proper relay, fuse, wiring, and mounting requirements or professional installation.
Skip If
- Your vehicle has very limited space behind the grille or bumper.
- You want a low-current, direct plug-in replacement with no wiring work.
- Your vehicle does not use a 12 V electrical system.
Design and Build Quality
The B133 uses the familiar HELLA SuperTone appearance: a black metal housing with a bright red protective grille. Each horn has a 123 mm diameter, so the pair has a noticeable physical footprint compared with many compact OEM horns.
The design is intended for exposed automotive use. HELLA lists IP65 protection and an operating temperature range from -40 °C to +60 °C. That gives the horn useful resistance to dust and water exposure, although installation location still matters. You should not mount electrical connectors where they are likely to sit in standing water or contact moving components.
Performance and Sound Quality
The main reason to choose the B133 is sound output. HELLA rates it at 118 dB(A), with one horn tuned to 300 Hz and the other to 500 Hz. The wide separation between the low and high tones helps create a distinct warning sound rather than a thin single-frequency beep.
The 300 Hz horn provides the deeper portion of the signal, while the 500 Hz horn adds the sharper tone that helps the sound remain noticeable around road and engine noise. The result is intended for warning other road users, not for continuous operation.
Mounting can influence how clearly the sound projects. Avoid burying the horn behind thick panels or placing its opening where debris can collect. A rigid mounting point also matters because vibration or a loose bracket can reduce reliability and create unwanted rattling.
Fit, Compatibility, and Installation
The B133 is a universal-style 12 V horn rather than a vehicle-specific plug-and-play assembly. Before ordering, measure the available space and compare it with the horn’s 123 mm diameter, 125 mm width, 135 mm overall height, and 85 mm depth.
Electrical capacity is equally important. HELLA’s technical information lists 66 W and a maximum current of 5.5 A per horn. Because both horns operate together, your wiring and control circuit need to be sized for the combined load rather than treated like a small low-current accessory.
The horn uses flat blade-style electrical contacts. Your vehicle may require a relay, suitable fuse protection, appropriate wire gauge, connectors, and mounting hardware depending on the original horn circuit and installation layout. Follow your vehicle wiring information and HELLA’s installation guidance, or use a qualified installer if you are not confident working on automotive electrical systems.
Before You Buy: Check the exact part number. HELLA lists 3AG 003 399-801 as the standard B133 SuperTone set, while 3AG 003 399-821 is a different B133 package that includes a 5-pin relay. Do not assume the 3AG 003 399-801 package includes the relay unless the seller specifically states it.
How It Performs in Real Use
For Daily City Driving
In city traffic, the B133’s biggest advantage is its strong dual-frequency warning signal. The combination of low and high tones is designed to stand out when surrounding traffic, engines, and general road noise make a weak factory horn difficult to hear.
For Highway Driving
At higher road speeds, wind and tire noise can mask quieter warning signals. The B133’s 118 dB(A) rating gives it strong acoustic output, but you should still use the horn only as a safety warning and according to local traffic laws.
For Off-Road and Utility Use
HELLA specifically promotes the B133 for demanding and off-road environments. The metal construction, protective grille, IP65 rating, and broad operating temperature range make it better suited to harsh automotive conditions than a basic decorative horn.
For Long-Term Ownership
HELLA specifies a service life of 100,000 cycles under ECE R28 testing. Long-term reliability still depends on installation quality. Secure brackets, protected terminals, correct wiring, and keeping the horns clear of heavy debris can all help prevent avoidable problems.
Installation Tips for Better Results
- Measure first: Confirm that both 123 mm horns can fit without touching the radiator, fan, bumper, grille, or other moving parts.
- Use a rigid mounting location: A solid bracket reduces vibration and helps keep each horn correctly positioned.
- Plan for the electrical load: Do not assume the original factory horn wiring can safely handle the pair without checking the circuit.
- Protect the connections: Use suitable automotive connectors and keep terminals away from locations where water can pool.
- Verify part number and package contents: The 3AG 003 399-801 and relay-equipped 3AG 003 399-821 are not the same package.
- Test before final assembly: Confirm both the 300 Hz and 500 Hz units operate before reinstalling trim or bumper components.
Pro Tip: Measure the horn cavity with the grille, bumper, and nearby wiring in mind, not just the flat mounting surface. The 123 mm diameter is only one part of the space requirement.
Compatibility and Safety
The B133 is built for a 12 V automotive electrical system. A vehicle having a 12 V battery does not automatically guarantee that the existing horn circuit, connector, fuse, and mounting location are suitable for this horn set.
HELLA lists ECE approval and compliance with ECE R28 for the B133. That certification does not replace local vehicle regulations, inspection rules, or installation requirements in your area. You should confirm any local restrictions before changing factory safety equipment.
Because the pair can demand substantial current, poor wiring can create voltage drop, unreliable horn operation, overheated wiring, or blown fuses. If you are unsure how to size the circuit or integrate a relay, professional installation is the safer choice.
Pros and Cons
Pros
- Strong 118 dB(A) sound output.
- 300 Hz and 500 Hz dual-tone design creates a distinctive warning signal.
- IP65 protection suits exposed automotive installations.
- ECE approved and designed to fulfil ECE R28 requirements.
- Metal housing and protective grille are designed for demanding vehicle use.
Cons
- The 123 mm housings may be too large for tight factory horn locations.
- Electrical demand is higher than many simple OEM horn replacements.
- The 3AG 003 399-801 package should not be assumed to include the relay supplied with the separate -821 variant.
Is It Worth the Price?
The B133 makes the most sense when sound output, build quality, and a recognizable dual-tone signal matter more to you than getting the smallest or simplest horn upgrade. Its 118 dB(A) output, 300/500 Hz pairing, IP65 protection, and ECE R28 specification give you concrete reasons to consider it beyond appearance alone.
The main value limitation is installation effort. You may need additional electrical components, wiring work, and extra mounting space, so the horn itself is only part of the upgrade. It is worth considering if you want the B133’s strong warning signal and your vehicle can support the installation, but it is not the best fit if you want a direct low-current replacement.
How It Compares to Alternatives
Within HELLA’s range, the M26 Sharp Tone set is a useful alternative for tighter installations. HELLA lists that set at 115 dB(A), 350/415 Hz, 42 W, and about 108 mm in diameter, so it is smaller and less demanding than the B133 but also has a lower specified sound level.
The HELLA B36 is another option, with a listed 116 dB(A) output and 335/400 Hz tones. The B133 remains the stronger choice when you specifically want the 118 dB(A) SuperTone output and wider 300/500 Hz frequency pairing.
Frequently Asked Questions
Is a relay included with the HELLA B133 3AG 003 399-801?
Do not assume so. HELLA separately lists part 3AG 003 399-821 as the B133 package that includes a 5-pin relay, which distinguishes it from the 3AG 003 399-801 set reviewed here. Check the seller’s package contents before ordering additional wiring parts.
Does the B133 include a mounting bracket?
HELLA’s B133 documentation describes the series with a metal bracket for M8 mounting. Package contents can differ between regional or marketplace listings, so confirm the seller’s photos and included-parts list before installation.
Will the HELLA B133 fit any 12 V car?
No. The voltage may be compatible with many vehicles, but you still need enough physical space, suitable mounting points, and an electrical circuit capable of handling the load. Measure the installation area and check your vehicle wiring before buying.
What frequencies does the B133 use?
The low-tone horn operates at 300 Hz and the high-tone horn at 500 Hz. These two frequencies work together to create the B133’s characteristic dual-tone signal.
How loud is the HELLA B133?
HELLA lists a sound level of 118 dB(A) for the B133. The manufacturer’s technical brief specifies sound-pressure testing at a distance of 2 meters, so the rating should not be compared directly with products measured using a different method or distance.
Can the B133 be installed on a motorcycle?
The B133 uses a 12 V electrical system, but it is not a motorcycle-specific plug-in horn. Its physical size and electrical demand may make it unsuitable for many motorcycles, so verify available space, charging capacity, wiring, and applicable regulations before considering that use.
What is the warranty period?
A fixed warranty period for this exact 3AG 003 399-801 marketplace listing was not verified for this review. Warranty coverage can depend on the seller, country, and HELLA regional policy, so check the current warranty terms before purchasing.
Does the B133 need regular maintenance?
It does not require routine servicing like a mechanical engine component, but occasional inspection is sensible. Check that mounting hardware remains tight, electrical terminals are secure, and dirt or debris is not interfering with the horn or wiring.
The Bottom Line
The HELLA B133 SuperTone Horn Set is a strong choice when you want a 12 V dual-tone horn with 118 dB(A) output, rugged construction, and a clear 300/500 Hz warning signal. It suits drivers who can accommodate the two 123 mm housings and proper electrical installation, while buyers wanting a tiny plug-in replacement should consider a more compact, lower-load alternative.
