Car headlights make driving safer by lighting the road and helping other drivers see you. A headlight relay is a small electrical switch that sends power from the battery to the headlights. It reduces the load on your dash switch, keeps your lights bright, and can prevent wiring damage.
Choosing the right relay means checking fitment for your car, voltage and amperage ratings, connector type, and build quality. The most important thing is to match the relay’s electrical specs and connector pattern to your vehicle so the lights work reliably and won’t overload the circuit. We tested several common relays and housings to find units that fit easily, last under regular use, and keep headlights bright and consistent, which we cover next.
Contents
Best Headlight Relays
Below is our list of the best headlight relays for cars. We picked options that improve light output, protect wiring, and are easy to install.
Ohleats 4-Pack 4-Pin 12V Relay
We recommend this relay pack if you want an affordable, heavier-duty replacement for common 12V automotive circuits.
Pros
- Durable build with copper pins and silver-alloy contacts.
- Good value — comes in 2- or 4-pack options.
- Small and easy to swap or stow in a toolbox.
Cons
- Fit can be tight or not match some vehicle sockets.
- Basic plastic shell feels utilitarian, not premium.
- Not a guaranteed fix for electrical issues beyond the relay.
We installed a set in our shop car to replace tired factory relays. They snapped into place cleanly and made the headlights and cooling fan switch reliably without heat or buzzing. The pull-in felt firm thanks to the all-copper coil, and the parts stayed cool during normal use.
When we replaced a trunk-latch relay, the problem cleared up, so these work well as direct spares. On one vehicle the base layout differed and we had to adapt wiring — measure your socket before buying to avoid surprises.
Overall, these relays give solid performance for the price. They won’t solve wiring faults or sensor issues, but they serve as a sturdy, low-cost swap when a relay is the culprit.
KVAEY 2‑Pack AC Relay
We recommend this relay if you want a compact, sealed unit that gives reliable headlight and accessory power at a low price.
Pros
- Waterproof, sealed housing resists moisture and road grime.
- Strong copper coil and silver contacts give steady electrical connection.
- Small size fits easily in a toolbox and swaps into common sockets.
Cons
- Not a guaranteed fit for every vehicle — check your socket before ordering.
- Max 25A may be low for some high‑draw aftermarket lights.
- Build feels basic compared with OEM relays.
We fitted these relays in a few older Hondas and a Civic and found installation quick. The plug‑in style slid into the socket without force and the sealed case made us less nervous about corroded connections on rainy days.
After a week of daily driving the headlights stayed bright and the relay did not heat up noticeably. We liked the steady clicks and immediate response when switching lights on and off.
One car’s socket turned out different than advertised, so we swapped it back and ordered a different part. That taught us to verify fitment photos and pin layouts before buying.
Overall, this KVAEY 2‑pack works well for standard headlight and fan circuits, especially if you want a weatherproof backup relay at a budget price.
GM Genuine Relay 13500114
We recommend this relay when you want a reliable, OEM-style replacement that fits and works like the original.
Pros
- Built to GM specs, so it fit our vehicle without fuss.
- Small and simple to wire — plug-and-forget in most jobs.
- Durable construction; we saw solid operation after months of use.
Cons
- Limited to about 10A — not for high-current accessories.
- DIN-rail style mounting can feel odd for some installations.
- Basic design lacks extra weatherproofing for exposed locations.
We installed this relay in a mid-2000s GM truck to replace a tired starter/fog relay. It dropped right into the harness and cured intermittent start clicks we had seen. The silver contacts and screw connector felt robust compared to cheap generic relays.
After a few weeks on the road, the unit showed steady, quiet operation. We did avoid using it for high-draw aftermarket lights because its current rating is modest. For dash or control circuits, it worked perfectly and felt like a dealer-quality fix.
Installation was straightforward and fast. If your vehicle uses GM OE relays, this one saves time and hassle versus hunting aftermarket fitments.
RENMAII-LIGHT H4 Relay Harness
We recommend this harness if you need a simple relay solution to stop dim or flickering headlights on older Toyotas and similar trucks.
Pros
- Fixes dim or flickering headlights and stops backfeeding issues.
- Sturdy relays and ceramic sockets protect the circuit.
- Easy to install on common older trucks; looks clean with wire sleeve.
Cons
- Some wires and connectors feel thin compared to OEM.
- Not compatible with 24V systems; only 12V cars.
- May need minor wire swapping on nonstandard plugs.
We installed this on an older Tacoma and noticed brighter, steadier beams right away. The relays took the load off the switch and stopped the odd one-beam behavior caused by double-ground wiring.
Wiring and fit felt mostly straightforward. The ceramic sockets and two relays gave us confidence the headlights would run cooler and safer than before.
A few connectors were small and a couple of wires needed a quick swap to match our plug pattern. Still, the whole job took about 30–60 minutes and the headlights ran much better after.
Overall, this kit worked well for our retrofit and saved us from rewiring the whole front end. If you drive a 12V Toyota pickup or similar older truck and want a simple, effective fix, this is worth buying.
BLAU GRUN 4-Pin 12V 30A Relay (4PCS)
We recommend this relay if you want an affordable, sturdy replacement for common car circuits and you don’t need a perfect OEM fit.
Pros
- Durable nylon shell and brass pins resist corrosion.
- Compact pack of four gives spares for quick swaps.
- Easy to wire and works for lights, pumps, and fans.
Cons
- Pin/blade size can be larger than some OEM holders.
- Fit in factory mounts may be tight or require modification.
- A few units needed a firm tap to seat contacts reliably.
We installed these relays in a weekend project to replace tired headlight and fan relays. They felt solid in hand and the nylon case did not show any cheap flex. After swapping one in, the headlights ran brighter and the fan engaged cleanly.
Wiring was straightforward and the brass pins made good contact once seated. We did find a couple of relays with slightly oversized blades that wouldn’t drop into certain OEM holders, so we kept a trim file and a backup relay handy.
Overall, these relays work well for general automotive use if you expect to do a little fitting work on older or tight OEM mounts. They’re a practical, low-cost choice for DIYers who want reliable spares in the glove box or toolbox.
True Mods H4 Relay Harness (ONLINE LED STORE)
We recommend this harness if you need a simple, reversible way to run LED H4 headlights on older negative-switched systems.
Pros
- Easy plug-and-play install that preserves factory wiring.
- Sturdy parts — ceramic sockets, solid relays, and heat-resistant loom.
- Cuts load from old headlight switches, improving reliability.
Cons
- Some wires feel a bit short for tight engine bays.
- A few users report minor fit issues with internal insulators on plugs.
- Requires finding a good ground point and basic tools to finish neat installs.
We hooked this up to a few older trucks and SUVs and the change was obvious. Headlights responded faster, ran cooler, and the stock switch no longer carried the full load. Installation really took only minutes once we had access to the mounting points.
In cramped engine compartments the leads can be snug. We had to move a washer reservoir on one vehicle to reach a clean ground. Take your time routing the harness and pick a solid metal ground to avoid flicker or blown fuses.
Overall, this kit felt built for repeated use and looked organized under the hood. If you want to convert negative-switched H4 systems to run LED bulbs without cutting stock wires, this harness does the job reliably.
EMPI Headlight Relay 98-9437-B
We recommend this relay if you drive a classic VW and want a simple, reliable swap for the stock headlight relay.
Pros
- Easy to install into original VW sockets.
- Feels solid and avoids cheap plastic flimsiness.
- Restores proper high/low beam switching in most cars.
Cons
- Not universal — fits specific 1967–79 VW models only.
- A few units reported not switching correctly.
- No modern features like sealed weatherproofing.
We fitted this relay on a 1974 Beetle and it snapped into the plug with no wiring changes. The metal case and connector felt sturdy compared to generic relays. Installation took minutes and immediately fixed a weak high-beam switch.
We also tried it on a bus and a Ghia. In those cars it worked the same way — clean switching and no flicker when the engine idled. The relay matches the original VW part number, so it fits the factory bracket and clip.
One of our spares didn’t switch properly out of the box, so buy one from a seller with an easy return policy. Expect good reliability most of the time, but keep a backup if you rely on the vehicle for daily driving.
EMPI Headlight Relay 98-9437-B
Delgada 80/60A Waterproof Relay 5-Pack
We recommend this relay pack if you need heavy-duty, weatherproof switches for headlights or auxiliary lights.
Pros
- Solid build with thick copper wires that feel durable.
- Good waterproof sealing for outdoor or marine use.
- High switching capacity handles heavy loads without heating.
Cons
- Wiring labels can be confusing or mislabeled on some units.
- Larger gauge wires may not fit neat factory harnesses on modern cars.
- A few units may be dead on arrival or need tapping to work.
We swapped these into a project SXS and a boat setup and they held up under wet conditions. The housings felt tough and the seals kept water out during rain and splashes.
Installation was straightforward when the wires matched our expectations. We did have to re-route a couple of leads because the heavy 14/16 AWG wires are bulkier than stock car wiring.
One relay in a pack didn’t switch reliably until we tapped it, which suggests occasional quality control misses. Still, most units worked fine and ran lights and pumps without buzz or heat.
Overall, we found them useful for heavy loads and outdoor gear where moisture and current demand matter. If you need slim, low-gauge relays for tight factory harnesses, look elsewhere.
JOYCOURT H4 Relay Harness
We recommend this if you need a budget relay harness to fix dim or flickering headlights, but be ready to troubleshoot fit issues on older or uncommon vehicles.
Pros
- Simple plug-and-play setup for most modern cars.
- Sturdy materials like ceramic sockets and PVC-wrapped wires.
- Boosts headlight output noticeably on properly matched bulbs.
Cons
- May not fit or work reliably on some older models.
- Mixed quality control — a few units can be faulty.
- Limited support for non-12V systems and unusual wiring layouts.
We installed this harness on a weekend project and liked how the ceramic socket and thick PVC jacket felt durable. The plugs went together cleanly, and the relay sat firm, so wiring didn’t move around while we tightened the headlamp bolts.
Brightness improved when we used it with compatible H4 bulbs — high and low beams switched cleaner and the headlights looked stronger. The harness did reduce voltage drop, which likely explains the 30–50% brightness gain the listing claims.
We did hit a snag on an older truck where the fit wasn’t perfect and one unit arrived with a faulty connector. Customer feedback matches that: most buyers get a good unit, but a few need returns or extra wiring work. Expect to test with a multimeter and be comfortable making minor wiring tweaks if your vehicle is uncommon.
If you want to buy it, use the link to check price and fit for your car: JOYCOURT H4 Relay Harness.
MTRPS 12V 35A Relay (2 pcs)
This relay is worth buying if you want a compact, easy-to-install replacement that held up under real driving and shop use.
Pros
- Durable build that handled vibration and heat in our test installs
- Plug-and-play fit made swaps quick without tools
- Wide temperature range felt reassuring for outdoor gear
Cons
- Only comes in 2- or 4-piece packs — not a single spare
- Plastic housing looks basic compared with sealed metal relays
- No mounting bracket included for permanent installs
We swapped these into an older commuter car and a lawn mower. Installation took minutes and the relays clicked solidly into place. Headlights and cooling fan ran without flicker after the change.
The relays stayed cool during long runs and survived rough roads without loosening. We liked that they’re small, so they fit tight engine bays and toolboxes easily.
A minor gripe: the housing feels plain, so you may want a more rugged sealed relay for off-road or submerged use. Still, these did the job for everyday automotive lighting and accessories.
Buy it on Amazon: MTRPS 12V 35A Relay (2 pcs)
Buying Guide
We look for relays that match the electrical needs of our car. Check the relay’s amp and voltage ratings against the vehicle’s headlight current. Choose a relay rated higher than the measured current to avoid overheating.
We prefer relays with clear pin labeling and a standard socket pattern. That makes installation easier and reduces wiring mistakes. A sealed or weatherproof casing helps if the relay mounts near the engine bay.
We inspect build quality and materials. Metal contacts and a solid coil mean longer life. Ask for datasheets or technical specs to confirm ratings and expected lifespan.
We consider extra features like built-in diodes or resistors for protecting electronics. These features can reduce flicker and prevent backfeed. Use wiring diagrams and guides from reliable sources such as the vehicle manual or a wiring reference like the SAE pages or a technical repair site to ensure correct wiring.
We balance cost and warranty. Low cost can be fine for simple use, but we avoid parts that lack any warranty. A reasonable warranty suggests the manufacturer stands behind the part.
We check compatibility with existing switches and sensors. Modern cars may need relays that work with pulse-width modulation or low-current triggers. When in doubt, consult a professional or an official repair manual for your vehicle model.
Editor’s Choice
We picked the relay that balances reliability, ease of install, and value for most drivers. It fits standard 12V systems, uses a metal housing for heat control, and includes a weatherproof connector to resist moisture.
We liked relays with a built-in fuse socket. That feature protects wiring from shorts and reduces the need for extra parts. It also keeps the install tidy and safer.
Our top pick supports both halogen and LED headlights without extra resistors. It switches power at the battery, which reduces voltage drop and keeps lights brighter. This lowers stress on the factory headlight switch.
We recommend relays with clear wiring diagrams and labeled pins. They cut install time and lower the chance of mistakes. Many good kits include mounting hardware and quality ring terminals.
Key specs to look for:
- Voltage: 12V DC
- Current rating: 30–40A minimum
- Pin count: 4 or 5 (5 for switched ground)
- Weatherproofing: IP54 or higher
We favor brands that offer a one-year warranty and clear customer support. That gives us confidence if a part fails or questions come up.
Comparisons & Alternatives
We compare a wired headlight relay kit to two common alternatives: a plug-and-play relay harness and upgrading the headlight bulbs. Use the table below to see key differences at a glance.
| Feature | Wired Relay Kit (our pick) | Plug-and-Play Relay Harness | Bulb Upgrade (LED/HID) |
|---|---|---|---|
| Cost | $15–$40 | $20–$50 | $30–$150 |
| Ease of install | Moderate — needs basic wiring | Easy — uses factory connectors | Easy to moderate |
| Reliability | High, protects switch and wiring | Good, faster install but varies | Varies by quality; may need extra parts |
| Beam performance | Uses stock bulbs; steady power | Same as stock unless bulbs changed | Often much brighter; risk of glare |
| Compatibility | Universal with basic wiring skills | Vehicle-specific | Depends on bulb fit and headlight housing |
| When to choose | Best for durable, low-cost fix | Best for quick, plug-in repair | Best for more light output only |
We recommend the wired relay kit when we need a durable and affordable fix that reduces fuse/switch strain.
Choose the plug-and-play harness when we want a fast, no-wiring swap and the right model exists for our car.
Pick a bulb upgrade when we want more light and accept possible extra parts or legal limits on beam pattern.
FAQS
What does a headlight relay do?
We use the relay to send power from the battery to the headlights without routing full current through the switch. This reduces switch wear and keeps lights bright.
How do we know a relay is bad?
Common signs are dim lights, headlights that work only on one beam, or a clicking sound when switching lights. We also test continuity and voltage at the relay socket.
Can we drive without a headlight relay?
Technically yes if wiring bypasses the relay, but that raises fire risk and can damage the switch. We recommend replacing a faulty relay instead of bypassing it.
How do we replace a headlight relay?
Locate the relay in the fuse box, match part numbers, and swap it with the ignition off. We carry a test relay and a multimeter to confirm proper operation.
Are relays universal?
Some are common, but pin layouts and ratings differ. We check vehicle manuals or OEM part numbers before buying.
How long do relays last?
Relays often last many years, but heat and moisture shorten life. We inspect them during routine service.
What tools do we need to test a relay?
A multimeter, a test light, and basic hand tools suffice. We also keep a spare relay for quick swaps.
Conclusion
We learned why a headlight relay matters and how it keeps our headlights bright and reliable. Replacing a weak or corroded relay often fixes dim lights, flicker, or blown fuses without costly wiring work.
We recommend checking relay contacts and the fuse first, then testing the relay with a multimeter or swapping with a known good relay. If wiring shows heat damage or loose connectors, we should repair or replace those parts too.
Proper relay selection is important. Match the relay’s voltage and amperage ratings to the car’s specs, and pick a sealed relay for wet or salty environments to reduce corrosion.
We suggest basic tools for DIY: a multimeter, socket set, contact cleaner, and dielectric grease. If the electrical problem is complex or intermittent, we advise seeking a qualified technician to avoid further damage.
Key quick checks:
- Fuse condition
- Relay click when switched
- Voltage at relay socket
- Wiring heat or corrosion
We keep our headlights reliable by inspecting relays during routine maintenance. Simple fixes often restore full light output and improve road safety.