How to Repair a 99 Honda Accord Main Relay Switch

Is your 99 Honda Accord experiencing starting issues? It could be due to a faulty main relay switch. The main relay switch is an important component of your vehicle’s electrical system, responsible for supplying power to the fuel injectors, ignition system, and other crucial components. When the main relay switch malfunctions, it can prevent your Accord from starting or cause intermittent starting problems.

In this article, we will guide you through the process of repairing the main relay switch in your 99 Honda Accord. Whether you are a DIY enthusiast or simply want to save on repair costs, this step-by-step guide will help you get your Accord up and running smoothly again.

Identifying the Main Relay Switch

The main relay switch in a 99 Honda Accord is located underneath the driver’s side dashboard. It is usually mounted on the metal bracket near the steering column. To access the main relay switch, you will need to remove the lower dashboard panel by unscrewing the screws or clips holding it in place.

Once you have removed the lower dashboard panel, you will be able to see the main relay switch. It is a small black or brown rectangular box with a wiring harness connected to it. The main relay switch in a 99 Honda Accord is known for its susceptibility to solder cracks, which can cause intermittent starting problems.

Now that you have located the main relay switch, let’s move on to the repair process.

Repairing the Main Relay Switch

Repairing the main relay switch in a 99 Honda Accord involves soldering the cracked solder joints. This process requires some basic soldering skills and the following tools:

• Soldering iron
• Solder wire
• Desoldering pump or wick
• Flux (optional)
• Isopropyl alcohol and a clean cloth

Before you begin the repair process, make sure to disconnect the negative terminal of your car battery to prevent any electrical mishaps.

Step 1: Removing the Main Relay Switch

Start by carefully disconnecting the wiring harness from the main relay switch. You may need to use a small flathead screwdriver or a pair of pliers to gently pry it off. Once the wiring harness is disconnected, you can remove the main relay switch from its mounting bracket.

Pro Tip: Take a picture or make a note of the wiring harness connections to ensure proper reinstallation later.

Step 2: Preparing the Main Relay Switch

With the main relay switch removed, inspect it for any visible signs of solder cracks. Cracks are usually found around the solder joints and can appear as hairline fractures. If you detect any cracks, it’s time to proceed with the repair.

Pro Tip: If you don’t see any cracks but are experiencing starting issues, you can still try reflowing the solder joints as a preventive measure.

Step 3: Reflowing the Solder Joints

Reflowing the solder joints involves melting the existing solder and allowing it to solidify again, effectively repairing any cracks. Follow these steps to reflow the solder joints:

1. Set up your soldering iron and let it heat up.
2. Apply a small amount of flux to the solder joints (optional). Flux helps improve the flow of solder and ensures a better bond.
3. Place the tip of the soldering iron on each solder joint and apply gentle pressure for a few seconds until the solder melts and flows smoothly.
4. Remove the soldering iron and allow the solder to cool and solidify.

Repeat this process for all the solder joints on the main relay switch. It’s important to be precise and avoid overheating the solder joints, as excessive heat can damage the switch.

Pro Tip: If you are new to soldering, practice on a scrap piece of electronic circuit board to get comfortable with the technique.

Step 4: Cleaning and Reinstalling the Main Relay Switch

After reflowing the solder joints, use a desoldering pump or wick to remove any excess solder or flux residue. Clean the main relay switch and the surrounding area with isopropyl alcohol and a clean cloth to ensure a clean and proper connection.

Once the main relay switch is clean, reinstall it onto the mounting bracket and reconnect the wiring harness. Make sure to double-check the connections against the picture or notes you took earlier.

Step 5: Testing the Main Relay Switch

Now that the main relay switch is repaired and reinstalled, it’s time to test it. Reconnect the negative terminal of your car battery and turn the ignition key to the “ON” position without starting the engine. Listen for a faint click sound coming from the main relay switch. This indicates that the relay is functioning properly.

If you hear the click sound and your Accord starts without any issues, congratulations! You have successfully repaired the main relay switch. However, if you still experience starting problems, you may need to consult a professional mechanic for further diagnosis.

Here’s a YouTube video that demonstrates the main relay switch replacement process on a 1998-2002 Honda Accord:

Conclusion

Repairing a faulty main relay switch in your 99 Honda Accord is a relatively simple task that can save you time and money. By following the steps outlined in this article and using the provided YouTube video tutorial as a visual guide, you can confidently undertake the repair process.

Remember to exercise caution when working with electrical components and always disconnect the car battery before starting any repairs. With a little patience and the right tools, you’ll have your Honda Accord running smoothly again in no time.

FAQs

1. How do I know if my main relay switch is faulty?

A: If your 99 Honda Accord experiences intermittent starting problems or fails to start at all, it could be a sign of a faulty main relay switch. Other symptoms may include the engine starting but immediately stalling or not starting after a hot soak.

2. Can I repair the main relay switch without soldering?

A: Soldering is the recommended method for repairing the main relay switch. However, if you don’t have soldering skills or equipment, you may consider replacing the entire main relay switch.

3. Is it necessary to disconnect the car battery before repairing the main relay switch?

A: Yes, it is essential to disconnect the car battery before working on any electrical components to avoid the risk of electrical shock or damage to the vehicle’s electrical system.

4. Can I use this repair method for other Honda models?

A: While the main relay switch repair process may differ slightly for other Honda models, the general concept remains the same. Consult your vehicle’s specific repair manual or seek professional advice for accurate guidance.

5. What if I still have starting issues after repairing the main relay switch?

A: If you have followed all the repair steps and still experience starting issues, it is recommended to consult a professional mechanic. There may be other underlying causes for the problem that require further diagnosis and repair.