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💡 Illuminate your night drives with zero flicker, zero hassle!
The KASLIGHT H4 Relay Harness Kit is a vehicle-specific wiring upgrade designed to fix dim and flickering headlights caused by dual ground issues in older Toyota Tacomas and similar models. It reroutes power directly from the battery through relays, supporting up to 360 watts and ensuring stable, bright LED or halogen headlight performance. Easy to install with durable connectors, this kit modernizes your lighting system while preserving your vehicle’s original aesthetics.






| ASIN | B07B9QQMMH |
| Auto Part Position | Inner |
| Automotive Fit Type | Vehicle Specific Fit |
| Best Sellers Rank | #32,661 in Automotive ( See Top 100 in Automotive ) #69 in Automotive Replacement Electrical Wiring Harnesses |
| Brand | KASLIGHT |
| Brand Name | KASLIGHT |
| Customer Reviews | 4.6 out of 5 stars 1,987 Reviews |
| Fit Type | Vehicle Specific Fit |
| Included Components | H4 Headlight Connector |
| Light Color | 4000K Cool White, 6500K Bright White |
| Light Source | Light Emitting Diode (LED) |
| Light Source Type | Light Emitting Diode (LED) |
| Manufacturer | KASLIGHT |
| Manufacturer Part Number | KAJE-0003 |
| Model Number | 8542081869 |
| Number of Pieces | 2 |
| Set Name | 1 Set |
| UPC | 653437481838 |
| Unit Count | 2.0 Count |
| Voltage | 12 Volts |
| Wattage | 360 watts |
A**A
Perfect to convert my Gen-1 Tacoma to halogen
I installed this kit on my '96 Tacoma over a year ago and it's been rock-solid ever since. I'm very happy with it. I bought it so that I could get away from the old old style sealed headlamps and adopt something more modern without changing the look of the vehicle. I opted for the Hella Vision Plus, which uses modern halogen bulbs that draw too much current for the original wiring. Enter this kit to solve the problem. Toyotas have a unique headlight wiring design that necessitates a compatible kit like this one, and it delivers. I like that the relays are totally solid, the wiring is easy, and the engine bay remains very clean. The components and wiring fit nicely right along the fender near the fuse box and the performance has been excellent, without any flickering and definitely without causing any stress to the original wiring, which carries far less current now -- just enough to power. The relays is all. Although this kit should work with any lighting solution you choose to add, I can also recommend the brightness and greater visibility provided by the Hella Vision Plus kit. I wish you the best of luck as you seek to upgrade the headlights on your vehicle.
A**L
Personal Experience with the H4 Relay Harness Kit: Solving My 1995 Toyota Tacoma’s Headlight Issues
As an owner of a 1995 Toyota Tacoma, I’ve experienced my fair share of electrical issues, particularly with the headlights. Over the years, I noticed my headlights weren’t as bright as they should be, and I was dealing with dim, flickering lights that weren’t just frustrating—they were also unsafe. After a lot of research, I decided to try the H4 Relay Harness Kit for my Tacoma, and it’s made a world of difference. Why I Chose This Kit The primary issue I faced with my truck’s headlights was the dreaded dual ground problem that many older vehicles, particularly Toyotas, tend to suffer from. This problem stems from the headlights drawing power directly from the stock wiring, which isn’t built to handle the higher current demand of modern, brighter bulbs. Over time, this can lead to dim lighting, flickering, or even failure of the headlight bulbs. The H4 Relay Harness Kit is designed to fix this issue by bypassing the stock wiring entirely, providing a direct, stronger power source from the battery to the headlights. I was looking for a solution that would not only improve the lighting but also prevent future electrical problems, and this kit seemed to be exactly what I needed. First Impressions When the kit arrived, I was impressed with how well it was packaged. The H6054 7x6 Polycarbonate Headlights were clear and seemed very durable. I was a little intimidated by the wiring aspect since I’m not the most mechanically inclined, but the instructions were straightforward, and I quickly realized I could handle the installation myself. The H4 relay harness itself is well-built, with high-quality wires and connectors that felt secure and sturdy. The dual ground fix was a major selling point, as it addressed the key issue that had been causing my problems in the first place. Installation Process The installation was a bit time-consuming but not overly complicated. After removing my old headlights and stock wiring, I followed the step-by-step instructions to install the relay harness. The most important part was making sure I correctly connected the dual ground wires, which can sometimes be tricky if you’re unfamiliar with automotive electrical systems. I’d recommend taking your time to ensure everything is properly connected. Once the wiring was complete, I attached the new headlights, which fit my 1995 Tacoma perfectly. The connectors clicked into place with no issues, and the entire process took me about two hours. The Results After installation, I couldn’t believe the difference. The lights were significantly brighter, and they stayed steady with no flickering. The true benefit, however, was the reliability. With the relay bypassing the stock wiring and providing direct power from the battery, my headlights now operate with consistent brightness without the strain on the original system. Driving at night is now a much safer experience. The improvement in visibility is noticeable, and I no longer worry about my headlights failing or dimming during a long drive. Why This Kit Works The key to why the H4 Relay Harness Kit is so effective lies in its design. By sending the current directly to the headlights from the battery, it bypasses the weak stock wiring, which often struggles with higher currents. This avoids the common dual ground problem that leads to voltage drops and dim lights in older vehicles. Additionally, the polycarbonate headlights are tough, resistant to road debris, and maintain their clarity over time. Paired with the relay harness, they deliver a significant upgrade over my old, aging headlights. Final Thoughts As someone who’s not an expert in car modifications but loves keeping my truck in good working condition, the H4 Relay Harness Kit was a fantastic choice. It solved a major electrical issue and improved my night driving experience. If you’re dealing with dim or flickering headlights, especially in older Toyotas like mine, this kit will solve your problem. Rating: 5/5 This kit delivered on every promise, and I’m thrilled with the results. Not only have I solved the dual ground problem, but I’ve also ensured that my headlights will continue to function reliably for the long haul. Highly recommend!
B**R
Simple. Effective. Amazing.
Vehicle: 1996 Jeep Cherokee Classic Overview: My headlight switch failed because it provides power to the headlights high/low beams through a factory wiring harness which is underpowered. The factory wiring harness is also the culprit of your dim lights. In my case, the headlight switch burnt up leaving me with no lights. Solution: I replaced the faulty switch and decided to upgrade to the H4 wiring harness. The H4 harness re-routes power to the headlights from the switch to the battery making the lights much brighter and removing the electrical load from the switch (while the switch no longer powers the headlights it will still function as your headlight switch.) Installation notes: The H4 wiring harness is truly plug-and-play. The only additional components I used were self-tapping screws, a piece of sandpaper for cleaning up the locations where I terminated my grounds, standard electrical tape, and a few extra cable ties. The overall length of the harness was plenty long for me. There wasn’t a whole lot of extra space to mount the relays next to the battery but it was doable. Had I simply taken 5 minutes to remove the battery it would have been a breeze. Total install time was about 90 minutes. Results: Noticeably brighter OEM headlights. Happy headlight switch and your vehicle will be ready for H4 aftermarket LED headlights (which you’re going to eventually do anyway right?) The harness itself comes with an in-line 30-amp breaker for your battery hookup and 2-80 amp relays. As an electrician by trade, I was impressed with the overall product quality. The crimps were strong and secure. The only thing that concerns me about this entire project would be the fact that the relays are not water-proof which may be an issue for the 4x4 crowd who would much prefer driving through a creek than over it. Final note: There are great install videos on YouTube if you are new to these things. Even for a novice DIY project, trust me, this is as simple and straightforward as the reviews indicate. Last comment, terminate your grounds correctly. Years of experience as a sparky, it’s not the harness that’s not working it’s because you didn’t land your grounds right.
A**E
Great kit!
Did what it needed to do! Includes everything but be aware that the included relays are not waterproof at all lol, rusted out and started giving me issues. Other than that very inclusive kit
M**.
Great quality
This product is fantastic, great quality easy to install worked perfectly in my 1965 Mustang.
F**K
87 Jeep Cherokee XJ - works great.
Installed in 1987 Jeep Cherokee XJ. Works great. Took about an hour to install due to tight spaces. I had the flickering/dead headlight problem- internet search told me it was the classic full-amperage headlight switch. I replaced the switch but also read about and wanted to use one of these kits to move the amps over to a relay to prevent it from getting all melty again, which after replacing the switch it was clear this was not the first time this issue happened on this vehicle. The switch wiring plug had already been replaced by the previous owner assumingly due to meltage. As some other reviews mentioned my only complaint is this harness could be about a foot longer in all directions. It was a very tight fit into the passenger headlight/battery area, but it did fit after 30 minutes of swearing or so. Lamp connectors are ceramic. 80amp! relays. 40amp fuse. Wiring is as big or bigger than stock and I plan to switch to led lights anyway once these old ones burn out. But yeah, for how cheap it is I am surprised it works as good as it does. I did make sure to check all the connections and wiggle all the wires to make sure they were snug in the little sockets. I am sure some folks get one that was loose at the factory but mine was fine all over. 10/10 Would recommend. Only had it working a day so will update in a few months with how its holding up.
N**N
5 min install and works great!
98 Toyota Tacoma, put new LED headlights in a work associates Tacoma they worked but they wouldn't brighten or anything. They were just on, so I looked up what we needed to do. I found this and told him this should fix them so they would function properly. Ordered it, got it the next day and installed it which was very simple. 5 min, well let's say 10 so no one says "oh u said it would only take 5 min, but it took 8 I'm suing u!" 🙄 Anyways after installation turned the lights on and wallah worked like a charm! Honestly the dim lights even looked brighter using this harness than they were using the factory wires... Bright and dim worked excellent! Would definitely recommend!
J**M
Works on 1991 Toyota Celica GTS, but...
This harness proved necessary because Toyota switches grounds while present day diode headlights switch power. This harness handles the conversion. I had no issues with the quality of construction and installation was as easy as it could be expected to be in the tight engine compartment and front end of this sports car. The headlights work fine. There is an issue however, which is why I have removed stars from my rating. Specifically, the car no longer has a high-beam indicator and, when I turn on the fog lamps, I am getting high beams out of the headlight rather than low beams. The problem appears to be that the low-beam side of the Toyota harness is expected to float high with current from the low-beam side of the headlight when the headlights are on in high beam, and it is this float-high that drives the high beam indicator AND turns off the fog lights when high beams are on. This relay package is disconnecting that section of wire and it is now open - neither high nor low - when the high beams are on. I did not generate a schematic of the harness before installing it, and to generate one now would pretty much require me to remove it in order to do that. This, I would rather not do. The problem should be simple enough to fix, but I really need a schematic of the harness in order to fix it. If the vendor will provide the schematic, I will update the review and add stars.
T**G
Works great!
Great product. Made my headlights brighter and was easy to install.
J**.
Excelente
excelente producto, trabaja muy bien.
A**O
Recomendable
Arregló mi problema de solo luces bajas y voltaje ya que brillan más mis luces led y facilita el manejo de noche.
D**N
Worth the price
Easy to install and allowed me to upgrade my lights
M**.
Quality
Excellent wire harness..I'm.very happy... I've ordered new led headlights from.ebsy. please note. One connection end is broken. The wires and connectors pulled out of ceramic base. Feels very cheaply made?
Trustpilot
1 week ago
2 weeks ago