How to Replace a Main Relay in a Honda Prelude

The main relay in the Honda Prelude helps to control the flow of high current within the ignition and fuel system. If your Honda Prelude has problems starting, the source of your problem may be this relay. In Honda Preludes manufactured between 1988 and 1991, locating and replacing the main relay can pose a challenge (compared to other Honda models from the same years), but isn't impossible.

Things You'll Need

• Manual or wiring diagram
• Pocketknife
• Ratchet, screwdriver and wrench sets
• Paper and pen
• Main relay replacement or kit
• Magnifying glass (optional)
• Soldering tools (optional)

Instructions

1. Determine the source of your starting problem by "listening" to your Honda Prelude. If you can't hear the main relay clicking (three times) when you attempt to start your car, then your problem likely stems from this relay. If the relay clicks, consider checking the fuel pump, ignition and other sources.

2. Disconnect the battery before working on any part of your Honda Prelude's electrical system as electrical surges and live wires can cause serious shocks and burns, damage surrounding systems, damage parts and wires and melt nearby plastic.

3. Find the main relay, marked "RELAY ASS'Y MAIN." Typically, it sits behind the dashboard to the left of the steering column in a section slightly up and behind a large section of wiring attached to the fuse panel.

4. Remove the coin tray and dashboard panel by releasing the coin tray tab with your pocketknife to get to this section. Take out any screws and then click the tabs that hold the panel in place until the panel comes out.

5. Disconnect any connectors or sockets, screws, bolts or nuts to get to the main relay. Make a list of each connection for future reference. Keep in mind that to get to the main relay in a Honda Prelude, you must unbolt the fuse panel and push aside any other devices or wires that block the main relay or make it difficult to reach.

6. Pull the fuse panel and main relay out and unplug the main relay from the connector or socket. Once disconnect the wiring from the relay, gently pull the main relay away from the panel by pressing in the tab with your pocketknife to release it. Repeat this process to remove the relay from its cover.

7. Pop the new relay into place by gently gripping the relay connector base and firmly pushing the relay into it without touching the solder components of the relay or the connector wiring. Check that the fit is secure, as current running through a loose relay can cause the relay to overheat or the outer casing to melt.

8. Reverse Steps 6 through 4 to reconnect the relay to the fuse panel, reinstall the fuse panel and return the dash area to normal. After tightening all nuts, bolts and screws, don't forget to reconnect the battery and start your Honda Prelude to confirm that the new main relay works.

Tips & Warnings

• Use the diagrams, schematics and pictures in a "workshop" or "repair" manual, instead of the manufacturer's manual that came with your Honda Prelude, to confirm the location of wiring and relays, switch direction placement and the correct flow of current.

• Check your main relay's solder for microscopic cracks with a magnifying glass before replacing it. Soldered joints can crack causing resistance in the relay and a voltage drop. Consider resoldering the joints to restore a non-working relay.