{"product_id":"s4784079292-genuine-wabco®-relay-valve-w-atc-kit","title":"S4784079292 | Genuine Wabco® Relay Valve W\/ATC Kit","description":"\u003cp\u003e\u003cstrong\u003eDescription\u003c\/strong\u003e:\u003cbr\u003eA \u003cstrong data-end=\"202\" data-start=\"187\"\u003erelay valve\u003c\/strong\u003e \u003cstrong\u003eS4784079292 \u003c\/strong\u003eis a type of valve in compressed air brake systems that helps \u003cstrong data-end=\"319\" data-start=\"265\"\u003espeed up the application and release of the brakes\u003c\/strong\u003e, especially on long vehicles like trailers. Without it, the air from the brake pedal would have to travel the full length of the vehicle to activate the rear brakes, which can be slow. Relay Valve W\/ATC Kit\u003cstrong\u003e\u003cspan\u003e \u003c\/span\u003e\u003c\/strong\u003eFor WABCO ABS\/air brake systems on trucks and buses, International, Freightliner, Volvo\/Mack, and other heavy truck platforms.\u003cbr\u003e\u003cbr\u003e\u003cstrong\u003ePart Number\u003cspan\u003e:\u003c\/span\u003e\u003c\/strong\u003e S4784079292\u003cbr\u003e\u003cstrong\u003eCondition\u003c\/strong\u003e\u003cspan\u003e: New\u003c\/span\u003e\u003cbr\u003e\u003cstrong\u003eManufacture\/Brand\u003c\/strong\u003e\u003cspan\u003e: Wabco\u003cbr\u003e\u003cstrong\u003eRelated Part Numbers: \u003c\/strong\u003eS478 407 929 2, TDA S478 407 929 2\u003cbr\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003c\/span\u003e\u003cstrong\u003eFits\u003cspan\u003e S4784079292 \u003c\/span\u003eFor \u003c\/strong\u003eWABCO ABS\/air brake systems on trucks and buses, International, Freightliner, Volvo\/Mack, and other heavy truck platforms.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong data-start=\"585\" data-end=\"597\"\u003ePurpose of using S4784079292:\u003cbr\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003ctable width=\"100%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp data-section-id=\"7oxnf6\" data-start=\"194\" data-end=\"226\"\u003e\u003cstrong data-start=\"198\" data-end=\"226\"\u003e1. Faster Brake Response\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"227\" data-end=\"486\"\u003e\n\u003cli data-section-id=\"1u7mtti\" data-start=\"227\" data-end=\"301\"\u003e\n\u003cp data-start=\"229\" data-end=\"301\"\u003eOn long vehicles, air has to travel from the brake pedal to rear brakes.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"82ujdy\" data-start=\"302\" data-end=\"393\"\u003e\n\u003cp data-start=\"304\" data-end=\"393\"\u003eA \u003cstrong data-start=\"306\" data-end=\"321\"\u003erelay valve\u003c\/strong\u003e receives the signal at the rear axles and applies air pressure locally.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"1fgkyp4\" data-start=\"394\" data-end=\"486\"\u003e\n\u003cp data-start=\"396\" data-end=\"486\"\u003e\u003cstrong data-start=\"396\" data-end=\"407\"\u003eResult:\u003c\/strong\u003e Rear brakes engage almost instantly, reducing stopping distance and brake lag.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-section-id=\"3aia28\" data-start=\"493\" data-end=\"530\"\u003e\u003cstrong data-start=\"497\" data-end=\"530\"\u003e2. Reduce Brake System Stress\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"531\" data-end=\"772\"\u003e\n\u003cli data-section-id=\"14jzskz\" data-start=\"531\" data-end=\"633\"\u003e\n\u003cp data-start=\"533\" data-end=\"633\"\u003eWithout a relay valve, the long air lines from the front to rear brakes could cause uneven pressure.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"18mq91v\" data-start=\"634\" data-end=\"717\"\u003e\n\u003cp data-start=\"636\" data-end=\"717\"\u003eThe relay valve \u003cstrong data-start=\"652\" data-end=\"673\"\u003ebalances pressure\u003c\/strong\u003e, so rear brakes don’t get over-pressurized.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"1vutxdj\" data-start=\"718\" data-end=\"772\"\u003e\n\u003cp data-start=\"720\" data-end=\"772\"\u003eThis \u003cstrong data-start=\"725\" data-end=\"751\"\u003eprevents wear and tear\u003c\/strong\u003e on brake components.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-section-id=\"5dy5sj\" data-start=\"779\" data-end=\"812\"\u003e\u003cstrong data-start=\"783\" data-end=\"812\"\u003e3. Traction Control (ATC)\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"813\" data-end=\"1071\"\u003e\n\u003cli data-section-id=\"1fl0xjo\" data-start=\"813\" data-end=\"875\"\u003e\n\u003cp data-start=\"815\" data-end=\"875\"\u003eThe \u003cstrong data-start=\"819\" data-end=\"834\"\u003eATC feature\u003c\/strong\u003e monitors wheel spin during acceleration.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"qr9ybl\" data-start=\"876\" data-end=\"1005\"\u003e\n\u003cp data-start=\"878\" data-end=\"1005\"\u003eIf a wheel starts slipping (like on ice or wet roads), the ATC uses the relay valve to \u003cstrong data-start=\"965\" data-end=\"990\"\u003emodulate air pressure\u003c\/strong\u003e to that wheel.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"cv4yl\" data-start=\"1006\" data-end=\"1071\"\u003e\n\u003cp data-start=\"1008\" data-end=\"1071\"\u003e\u003cstrong data-start=\"1008\" data-end=\"1019\"\u003eResult:\u003c\/strong\u003e Better grip, fewer accidents, more stable handling.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-section-id=\"1fdkavf\" data-start=\"1078\" data-end=\"1121\"\u003e\u003cstrong data-start=\"1082\" data-end=\"1121\"\u003e4. Integrated Safety and Efficiency\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"1122\" data-end=\"1277\"\u003e\n\u003cli data-section-id=\"uxn309\" data-start=\"1122\" data-end=\"1190\"\u003e\n\u003cp data-start=\"1124\" data-end=\"1190\"\u003eCombines \u003cstrong data-start=\"1133\" data-end=\"1150\"\u003equick braking\u003c\/strong\u003e and \u003cstrong data-start=\"1155\" data-end=\"1175\"\u003etraction control\u003c\/strong\u003e in one system.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-section-id=\"blx0gc\" data-start=\"1191\" data-end=\"1277\"\u003e\n\u003cp data-start=\"1193\" data-end=\"1277\"\u003eHelps drivers \u003cstrong data-start=\"1207\" data-end=\"1227\"\u003emaintain control\u003c\/strong\u003e in slippery conditions while reducing brake wear.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp data-start=\"585\" data-end=\"703\"\u003e\u003cstrong data-start=\"585\" data-end=\"597\"\u003e\u003cbr\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eSigns of Bad Relay Valve W\/ATC S4784079292:\u003c\/strong\u003e\u003c\/p\u003e\n\u003ctable width=\"100%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp data-end=\"181\" data-start=\"140\" data-section-id=\"qlh163\"\u003e\u003cstrong data-end=\"181\" data-start=\"144\"\u003e1. Slow or Delayed Brake Response\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"373\" data-start=\"182\"\u003e\n\u003cli data-end=\"233\" data-start=\"182\" data-section-id=\"1utsbgh\"\u003e\n\u003cp data-end=\"233\" data-start=\"184\"\u003eThe relay valve helps rear brakes engage quickly.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"373\" data-start=\"234\" data-section-id=\"qm59xc\"\u003e\n\u003cp data-end=\"261\" data-start=\"236\"\u003e\u003cstrong data-end=\"259\" data-start=\"236\"\u003eSigns of a problem:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"373\" data-start=\"264\"\u003e\n\u003cli data-end=\"304\" data-start=\"264\" data-section-id=\"1186405\"\u003e\n\u003cp data-end=\"304\" data-start=\"266\"\u003eRear brakes lag behind front brakes.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"373\" data-start=\"307\" data-section-id=\"1t35j3o\"\u003e\n\u003cp data-end=\"373\" data-start=\"309\"\u003eYou feel “spongy” or delayed braking when you press the pedal.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"414\" data-start=\"380\" data-section-id=\"1mvs3um\"\u003e\u003cstrong data-end=\"414\" data-start=\"384\"\u003e2. Uneven or Harsh Braking\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"590\" data-start=\"415\"\u003e\n\u003cli data-end=\"490\" data-start=\"415\" data-section-id=\"1gzpucn\"\u003e\n\u003cp data-end=\"490\" data-start=\"417\"\u003eA failing valve may cause some brakes to apply too hard or too lightly.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"590\" data-start=\"491\" data-section-id=\"m660am\"\u003e\n\u003cp data-end=\"504\" data-start=\"493\"\u003eSymptoms:\u003c\/p\u003e\n\u003cul data-end=\"590\" data-start=\"507\"\u003e\n\u003cli data-end=\"556\" data-start=\"507\" data-section-id=\"rd4aa4\"\u003e\n\u003cp data-end=\"556\" data-start=\"509\"\u003eThe vehicle pulls to one side during braking.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"590\" data-start=\"559\" data-section-id=\"jbzeeq\"\u003e\n\u003cp data-end=\"590\" data-start=\"561\"\u003eSudden jerks when stopping.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"650\" data-start=\"597\" data-section-id=\"1qj4350\"\u003e\u003cstrong data-end=\"650\" data-start=\"601\"\u003e3. Wheel Lock or Slip During Traction Control\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"826\" data-start=\"651\"\u003e\n\u003cli data-end=\"703\" data-start=\"651\" data-section-id=\"d1xl5l\"\u003e\n\u003cp data-end=\"703\" data-start=\"653\"\u003eATC controls air pressure to prevent wheel spin.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"826\" data-start=\"704\" data-section-id=\"7ovnf\"\u003e\n\u003cp data-end=\"720\" data-start=\"706\"\u003eIf it fails:\u003c\/p\u003e\n\u003cul data-end=\"826\" data-start=\"723\"\u003e\n\u003cli data-end=\"780\" data-start=\"723\" data-section-id=\"gfnfks\"\u003e\n\u003cp data-end=\"780\" data-start=\"725\"\u003eWheels may \u003cstrong data-end=\"777\" data-start=\"736\"\u003espin excessively on slippery surfaces\u003c\/strong\u003e.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"826\" data-start=\"783\" data-section-id=\"1cewn2u\"\u003e\n\u003cp data-end=\"826\" data-start=\"785\"\u003eVehicle may lose traction unexpectedly.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"853\" data-start=\"833\" data-section-id=\"h4tiye\"\u003e\u003cstrong data-end=\"853\" data-start=\"837\"\u003e4. Air Leaks\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"1075\" data-start=\"854\"\u003e\n\u003cli data-end=\"915\" data-start=\"854\" data-section-id=\"m8lfub\"\u003e\n\u003cp data-end=\"915\" data-start=\"856\"\u003eRelay valves have seals and diaphragms that can wear out.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1075\" data-start=\"916\" data-section-id=\"162z826\"\u003e\n\u003cp data-end=\"926\" data-start=\"918\"\u003eSigns:\u003c\/p\u003e\n\u003cul data-end=\"1075\" data-start=\"929\"\u003e\n\u003cli data-end=\"963\" data-start=\"929\" data-section-id=\"1jgtrz2\"\u003e\n\u003cp data-end=\"963\" data-start=\"931\"\u003eHissing sounds near the valve.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1012\" data-start=\"966\" data-section-id=\"1rpgilg\"\u003e\n\u003cp data-end=\"1012\" data-start=\"968\"\u003eAir pressure dropping in the brake system.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1075\" data-start=\"1015\" data-section-id=\"1ni79wp\"\u003e\n\u003cp data-end=\"1075\" data-start=\"1017\"\u003eBrake pedal feels hard to pump or doesn’t hold pressure.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"1121\" data-start=\"1082\" data-section-id=\"15ugw9f\"\u003e\u003cstrong data-end=\"1121\" data-start=\"1086\"\u003e5. Warning Lights \/ Error Codes\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"1286\" data-start=\"1122\"\u003e\n\u003cli data-end=\"1286\" data-start=\"1122\" data-section-id=\"2t5knc\"\u003e\n\u003cp data-end=\"1152\" data-start=\"1124\"\u003eOn modern trucks with ATC:\u003c\/p\u003e\n\u003cul data-end=\"1286\" data-start=\"1155\"\u003e\n\u003cli data-end=\"1204\" data-start=\"1155\" data-section-id=\"tcg5bd\"\u003e\n\u003cp data-end=\"1204\" data-start=\"1157\"\u003e\u003cstrong data-end=\"1186\" data-start=\"1157\"\u003eATC or ABS warning lights\u003c\/strong\u003e may illuminate.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1286\" data-start=\"1207\" data-section-id=\"vlvx3l\"\u003e\n\u003cp data-end=\"1286\" data-start=\"1209\"\u003eDiagnostic codes may indicate \u003cstrong data-end=\"1283\" data-start=\"1239\"\u003evalve malfunction or air pressure issues\u003c\/strong\u003e.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-end=\"1349\" data-start=\"1293\" data-section-id=\"1x4t56z\"\u003e\u003cstrong data-end=\"1349\" data-start=\"1297\"\u003e6. Slow Trailer Brake Response (if on a trailer)\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-end=\"1484\" data-start=\"1350\"\u003e\n\u003cli data-end=\"1484\" data-start=\"1350\" data-section-id=\"togjn4\"\u003e\n\u003cp data-end=\"1382\" data-start=\"1352\"\u003eOn vehicles towing trailers:\u003c\/p\u003e\n\u003cul data-end=\"1484\" data-start=\"1385\"\u003e\n\u003cli data-end=\"1431\" data-start=\"1385\" data-section-id=\"1a7udi2\"\u003e\n\u003cp data-end=\"1431\" data-start=\"1387\"\u003eRear or trailer brakes respond sluggishly.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"1484\" data-start=\"1434\" data-section-id=\"fohj4o\"\u003e\n\u003cp data-end=\"1484\" data-start=\"1436\"\u003eRelay valve may not be relaying air correctly.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp data-start=\"97\" data-end=\"476\"\u003e\u003cstrong data-start=\"97\" data-end=\"151\"\u003e\u003cbr\u003eAbout the Manufacturer – Wabco:\u003c\/strong\u003e\u003cbr data-start=\"151\" data-end=\"154\"\u003e\u003cstrong data-start=\"0\" data-end=\"9\"\u003eWABCO\u003c\/strong\u003e (originally the\u003cstrong\u003e \u003c\/strong\u003eWestinghouse Air Brake Company) is a global leader in vehicle control systems for commercial vehicles such as trucks, buses, and trailers. Founded in 1869 and later becoming a part of ZF Friedrichshafen AG in 2020, WABCO is best known for pioneering advanced braking, stability, and suspension technologies.\u003cbr\u003e\u003c\/p\u003e","brand":"Wabco","offers":[{"title":"Default Title","offer_id":50610990612727,"sku":"S4784079292","price":665.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0895\/7080\/3959\/files\/photo_2026-03-20_04-54-54.jpg?v=1773975980","url":"https:\/\/forcetruckparts.com\/products\/s4784079292-genuine-wabco%c2%ae-relay-valve-w-atc-kit","provider":"Force Truck Parts","version":"1.0","type":"link"}