㉦Mercedes Ke-Jetronic㉦ - Bad OVP Relay Symptoms on KE(Mercedes Cold Start & Idle Problems Explained)

In this video, I explain one of the most important (and most misunderstood) components in the Mercedes KE-Jetronic system: ✅ The OVP Relay (Overvoltage Protection Relay) Many classic Mercedes engines suffer from: Rough idle No cold start Sluggish acceleration when cold ABS warning light ECU losing power completely And very often, the real cause is a failing OVP relay. 🔧 What you will learn in this episode: What the OVP relay does and why Mercedes used it The difference between 6-pin, 7-pin, and 9-pin OVP versions Why the fuse burns out and what it protects Which terminals supply the ECU, idle valve (ICV), and ABS Common symptoms of a bad OVP relay Step-by-step diagnostic testing with a voltmeter ✅ Applies to Mercedes models with KE-Jetronic: W201 (190E) W124 W126 R107 / R129 Engines: M102, M103, M104 and more ⚠️ Key takeaway: If your ECU and idle control valve lose power, don’t touch the mixture screw yet… Check the OVP relay first! 📌 Support FixYourMercedes & get exclusive diagnostics on Patreon: 🔧 Master Mechanic Tier → (your link here) TIME CODES / CHAPTERS 0:00 – Greetings from Serbia (Don & Nicole 🇨🇦❤️) 0:45 – Today’s Topic: What is the OVP Relay? 1:40 – Different OVP Versions (6-pin, 7-pin, 9-pin) 3:10 – Fuse Inside the OVP: Why Mercedes Added It 4:30 – The Two Main Functions of the OVP Relay 6:00 – Terminal Explanation (30, 31, 15, 87E, 30A…) 8:15 – Why Overvoltage Can Destroy the ECU & ICV 9:40 – 7-pin vs 9-pin OVP (ABS / ASR Models) 11:20 – Symptoms of a Bad OVP Relay 12:50 – No Cold Start, Rough Idle, Sluggish Acceleration 14:10 – ABS Light On? Check Generator Voltage 15:00 – How to Test the OVP Relay (Voltmeter Method) 17:00 – Jumper Test: Terminal 30 to 87 18:20 – When to Replace the Relay vs Wiring Diagnosis 19:10 – Final Message + Happy Mercedesing! 🚗✨ Happy Mercedesing! 🚗✨