How to Fix a Relay in Your Car: A DIY Guide

Relays are essential components in your car’s electrical system, acting as switches that control higher current circuits using a lower current signal. If you’re experiencing electrical issues like a non-starting engine, malfunctioning fuel pump, or faulty headlights, a faulty relay could be the culprit. Instead of immediately replacing a potentially expensive relay, you might be able to fix it yourself with a few simple steps. This guide will walk you through the process of how to fix a relay in your car, potentially saving you time and money.

Understanding car relays is crucial before attempting any repairs. A relay is essentially an electromagnetic switch. It consists of a coil and a set of contacts. When a small electrical current is applied to the coil, it creates a magnetic field. This magnetic field then pulls a switch closed, allowing a larger current to flow through the relay’s contacts and power the intended component, such as a fuel pump or headlight. This mechanism allows low-current circuits to control high-current circuits, protecting sensitive switches and wiring.

Before you jump into fixing a relay, it’s important to diagnose if the relay is indeed the problem. Common symptoms of a bad relay include:

• Component not working: The most obvious sign is that the component controlled by the relay (e.g., fuel pump, horn, headlights) is not functioning.
• Clicking sound: A relay might click rapidly or erratically, indicating internal issues or insufficient power.
• Intermittent issues: The component works sometimes but fails at other times, suggesting a loose connection or failing relay.

To confirm a faulty relay, you can perform a simple test. Locate the relay in question (refer to your car’s repair manual for relay locations, often found in fuse boxes under the hood or dashboard). Once located, you can try swapping it with an identical relay from a less critical system (like the rear window defogger, if applicable). If the problem moves to the system where you moved the suspect relay, then the relay is likely faulty. Alternatively, you can use a multimeter to perform a continuity test to check the relay’s coil and contacts, but for a quick check, swapping is often faster.

Now, let’s get to the repair process. This guide focuses on fixing a common issue: a broken coil wire within the relay. This is a repair approach suitable for those comfortable with basic soldering and electronics.

Step-by-Step Guide to Fixing a Car Relay

1. Remove the Relay and its Cover: Carefully remove the suspected faulty relay from its socket. Relays usually pull straight out. Once removed, you’ll need to take off the relay’s plastic or metal cover. Some covers are designed to snap off, while others might be glued and require gentle prying with a small flathead screwdriver. Be careful not to damage the internal components while removing the cover.

2. Identify the Broken Coil Wire: Inside the relay, you’ll see a coil of thin wire wrapped around a core. Carefully inspect this coil for any breaks. Often, the break occurs at the point where the fine coil wire connects to a terminal post. Look for a loose or broken wire end. In many cases, the broken wire will be quite apparent upon close inspection.

3. Prepare the Wire for Resoldering: To fix the broken wire, you’ll need to resolder it. Gently unwind a very small length of the broken wire from the coil – just enough to work with. Use a tool like tweezers or fine-nosed pliers to carefully unwind one or two turns. You only need a minimal amount of extra wire to make a new connection.

4. Remove Insulation and Resolder: The coil wire is coated with a thin layer of insulation. You need to remove this insulation at the very end of the wire to ensure a good solder connection. You can use a спеціалізований wire stripper for fine wires, or carefully scrape off the insulation with the edge of a sharp blade or hobby knife. Be extremely gentle to avoid breaking the wire. Once the insulation is removed, carefully solder the wire back onto the terminal post where it was originally connected. Use a small soldering iron and rosin-core solder. Ensure a clean and solid solder joint.

5. Test the Repaired Relay: After soldering, let the relay cool down. You can now test if your repair was successful. Before reassembling the cover, you can perform a continuity test across the relay’s coil pins (typically pins 85 and 86). You should see a low resistance reading, indicating a completed circuit. To test the relay’s switching function, apply 12VDC to the coil pins (pin 86 positive, pin 85 negative). You should hear a click sound, indicating the relay is switching. For a more thorough test, check for continuity between the relay’s switch contacts (typically pins 30 and 87) when 12VDC is applied to the coil.

6. Reassemble and Reinstall: If the relay tests successfully, carefully reassemble the relay cover. Ensure it’s securely closed. Then, reinstall the repaired relay back into its original socket in your car. Test the component that was originally malfunctioning to see if the repair has resolved the issue.

Conclusion

Fixing a car relay with a broken coil wire can be a straightforward repair for those with basic electronics skills. By following these steps, you can potentially save yourself the cost of a new relay and get your car’s electrical system back in working order. While this DIY fix is effective for simple wire breaks, remember that relays can fail in other ways. If you’re unsure about the repair process or if the relay continues to malfunction after repair, it’s always best to consult a qualified automotive technician. However, for a quick fix of a broken coil wire, this guide provides a practical and potentially time-saving solution.