How Automotive Relays Work (And How to Wire Them Correctly)

🔧 In Today’s Video:
Automotive relays are simple devices, but they’re often misunderstood and wired incorrectly. In this video, I explain how automotive relays work and show the correct way to wire standard 4-pin and 5-pin relays for reliable operation in classic and modern vehicles.
Whether you’re adding headlights, electric fans, fuel pumps, or accessories, understanding relay operation is critical to preventing voltage drop, overheating, and electrical failures.

Topics Covered:
• What an automotive relay actually does
• How relay terminals work (30, 85, 86, 87, 87a)
• Difference between 4-pin and 5-pin relays
• Proper relay wiring methods
• Common relay wiring mistakes

0:00 - Overview- What is a Relay?
1:32 - Understanding How a Relay Works
3:07 - Relay Labeling and Identification
8:24 - 4 pin Relay Operation
8:51 – 5 pin Relay Operation
10:38 – Extra Nuggets!

🛠️ Tools & Parts Used in This Video
👉 Variable Output DC Power Supply: https://amzn.to/4qcTQw4
👉 Test Leads: https://amzn.to/4q8MZUk
👉 30 Amp 4 pin relay: https://amzn.to/3KWwxaN
👉 30 Amp 5 pin relay: https://amzn.to/4iYoIxY
👉 30 Amp 4 pin relay with connector and pigtail: https://amzn.to/48DXmtx

📚 Helpful Videos You Might Like
• How to Wire Starter Solenoids:    • How to Wire a Starter Solenoid  
• Ignition Cylinder Lock Removal:    • How to remove and replace GM, Ford and Mop...  
• Testing Turn Signal Switches:    • How to Decode and Test Turn Signal Switche...  

💬 Have a Question?
Leave a comment — I try to respond to as many as possible.
If you're working on a specific electrical issue, let me know what you're driving and what symptoms you’re seeing.

📸 Follow Me & My Projects
Facebook: https://www.facebook.com/profile.php?...

🔌 Want More Classic Automotive How-To Videos?
Subscribe here:    / @paulsvintagewiring  

🔑 Keywords
classic car wiring, vintage car electrical repair, ignition system troubleshooting, wiring harness diagnostics, automotive wiring tutorial, GM wiring, Ford wiring, MoPar wiring, starter solenoid wiring, turn signal switch testing, MSD ignition wiring, classic car restoration electrical, automotive relays explained

⚠️ Affiliate Disclosure
Some of the links above are affiliate links, meaning I may earn a small commission — at no extra cost to you. This helps support the channel and allows me to keep creating videos for the classic car community. Thank you!