{"product_id":"tekonsha-118578-modulite-4-way-flat-harness-t-one","title":"Tekonsha 118578 ModuLite 4-Way Flat Harness | T-One","description":"\u003cp class=\"nvn-hero\"\u003eThe Tekonsha 118578 is the plug-in fix when your OEM 4-way flat tow harness has had enough. It's a T-One connector paired with an upgraded, circuit-protected ModuLite module, so your trailer lights pull power straight from the battery instead of the vehicle's factory circuits. Clean signal, protected wiring, no cutting.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eIf you tow a boat trailer, you know the factory 4-way flat is often the first thing to give out. The Tekonsha 118578 is the replacement, and it's a T-One connector, which means it plugs straight into your vehicle's existing wiring harness. No splicing. No scotch-locks. No chasing a bad ground six months later.\u003c\/p\u003e\n\u003cp\u003eHere's what makes this one worth the money. The upgraded ModuLite module is a powered converter, not a simple splice-in tap. It pulls the current your trailer lights need directly from the battery, so your vehicle's factory light circuits never see the extra load. That matters on newer rigs where the taillight computer will throw a fault, or just quietly stop working, if you overload it. The module takes the hit instead.\u003c\/p\u003e\n\u003cp\u003eAnd it's circuit protected. If something on the trailer side shorts out, a corroded connector, a pinched wire, a bulb that finally lets go, the module protects the run rather than passing the fault back up into your vehicle's wiring. That's the upgraded part of the name doing real work.\u003c\/p\u003e\n\u003cp\u003eInstallation is about as painless as trailer wiring gets. You find the factory harness connector, unplug it, plug the T-One in between, and route the 4-way flat back to the hitch. Most folks are done in well under an hour with basic hand tools. Because it's a direct-fit T-connector, you're not guessing at wire colors or reading a factory diagram.\u003c\/p\u003e\n\u003cp\u003eOne thing to check before you order: fitment. This is a vehicle-specific T-One, so confirm the 118578 part number matches your exact year, make, and model before you buy. If you're not sure, send us the vehicle details and we'll tell you straight whether this is the right connector for your setup. We'd rather get you the right part the first time than have you fighting a harness that won't seat.\u003c\/p\u003e\n\u003cp\u003eFor a boat trailer running standard 4-way flat lighting, this is the clean, protected way to wire it up. Plug in, protect your vehicle's circuits, and get back to the ramp.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003e4-Way Flat output connector, the standard for boat trailers and small utility trailers\u003c\/li\u003e\n  \u003cli\u003eT-One plug-in design connects to your OEM harness with no splicing or cutting\u003c\/li\u003e\n  \u003cli\u003eUpgraded circuit-protected ModuLite module isolates your vehicle's factory light circuits from trailer-side faults\u003c\/li\u003e\n  \u003cli\u003ePowered converter draws trailer lighting current from the battery, so newer taillight circuits don't overload\u003c\/li\u003e\n  \u003cli\u003eDirect replacement for a worn or failed OEM tow wiring harness\u003c\/li\u003e\n  \u003cli\u003eVehicle-specific fit, installs in under an hour with basic hand tools\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cdiv class=\"nvn-trust\"\u003e\n  \u003ch2\u003eWhy Buy from NVN Marine\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eAuthorized Tekonsha reseller, full manufacturer warranty\u003c\/li\u003e\n    \u003cli\u003eNMEA member and ABYC certified, advice from real boat techs\u003c\/li\u003e\n    \u003cli\u003eSame-day shipping before 3 PM ET on in-stock items\u003c\/li\u003e\n    \u003cli\u003eNY headquarters and Fort Lauderdale flagship retail store\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"nvn-faq\"\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat does the ModuLite module actually do?\u003c\/summary\u003e\n    \u003cp\u003eIt's a powered converter. Instead of tapping your vehicle's factory light circuits, it pulls the trailer lighting current straight from the battery. That keeps the extra load off your taillight wiring, which matters a lot on newer vehicles that fault when overloaded.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDo I need to cut or splice any wires?\u003c\/summary\u003e\n    \u003cp\u003eNo. This is a T-One connector, so it plugs into your vehicle's existing harness. You unplug the factory connector, plug the T-One in between, and run the 4-way flat to the hitch. No scotch-locks, no wire cutting.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill this fit my vehicle?\u003c\/summary\u003e\n    \u003cp\u003eThe T-One is vehicle-specific, so confirm the 118578 part number against your exact year, make, and model before ordering. If you're not sure, send us the vehicle details and we'll check it for you.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat kind of trailer plug does it give me?\u003c\/summary\u003e\n    \u003cp\u003eA standard 4-way flat connector, which is what most boat trailers and small utility trailers use for running lights, brake, and turn signals.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat does circuit protected mean here?\u003c\/summary\u003e\n    \u003cp\u003eIf something shorts on the trailer side, a corroded pin, a pinched wire, a failed bulb, the module protects the circuit instead of passing that fault back into your vehicle's wiring. It's the safeguard that saves you an expensive repair up front.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow long does the install take?\u003c\/summary\u003e\n    \u003cp\u003eMost people finish in well under an hour with basic hand tools. Because it's a direct-fit plug-in, you're not reading a factory wiring diagram or matching wire colors.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable class=\"nvn-specs\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eTitle\u003c\/th\u003e\n\u003ctd\u003e4-Way Flat Replacement For OEM Wiring Harness With Upgraded Circuit Protected ModuLite Module\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eTekonsha\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer Part Number\u003c\/th\u003e\n\u003ctd\u003e118578\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e016118121667\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eConnector Type\u003c\/th\u003e\n\u003ctd\u003e4-Way Flat\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eModule\u003c\/th\u003e\n\u003ctd\u003eCircuit Protected ModuLite\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eConnection Type\u003c\/th\u003e\n\u003ctd\u003eT-One plug-in connector\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePower Source\u003c\/th\u003e\n\u003ctd\u003eVehicle battery (powered converter)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCircuit Protection\u003c\/th\u003e\n\u003ctd\u003eBuilt into the ModuLite module\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eFunction\u003c\/th\u003e\n\u003ctd\u003eDirect replacement for OEM 4-way flat wiring harness\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@type\": \"FAQPage\",\n    \"mainEntity\": [\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What does the ModuLite module actually do?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a powered converter. Instead of tapping your vehicle's factory light circuits, it pulls the trailer lighting current straight from the battery. That keeps the extra load off your taillight wiring, which matters a lot on newer vehicles that fault when overloaded.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Do I need to cut or splice any wires?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"No. This is a T-One connector, so it plugs into your vehicle's existing harness. You unplug the factory connector, plug the T-One in between, and run the 4-way flat to the hitch. No scotch-locks, no wire cutting.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will this fit my vehicle?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The T-One is vehicle-specific, so confirm the 118578 part number against your exact year, make, and model before ordering. If you're not sure, send us the vehicle details and we'll check it for you.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What kind of trailer plug does it give me?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A standard 4-way flat connector, which is what most boat trailers and small utility trailers use for running lights, brake, and turn signals.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What does circuit protected mean here?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"If something shorts on the trailer side, a corroded pin, a pinched wire, a failed bulb, the module protects the circuit instead of passing that fault back into your vehicle's wiring. It's the safeguard that saves you an expensive repair up front.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How long does the install take?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Most people finish in well under an hour with basic hand tools. Because it's a direct-fit plug-in, you're not reading a factory wiring diagram or matching wire colors.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"TEKONSHA","offers":[{"title":"Default Title","offer_id":45064333328477,"sku":"2008729","price":78.29,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_5426db16-2e2f-4e2b-9030-4da482b25dc2.jpg?v=1789595369","url":"https:\/\/nvnmarine.com\/products\/tekonsha-118578-modulite-4-way-flat-harness-t-one","provider":"NVN Marine","version":"1.0","type":"link"}