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MegaSquirt Relay Board - Assembled Unit
MegaSquirt Relay Board - Assembled Unit
MegaSquirt Relay Board - Assembled Unit
MegaSquirt Relay Board - Assembled Unit

MegaSquirt Relay Board – Assembled Unit

5 out of 5 based on 3 customer ratings
(3 customer reviews)



Don't forget the wiring!!

MegaSquirt Relay Cable

MegaSquirt Wiring Bundle - 8' Long


MegaSquirt Relay Board – Assembled Unit – Part# MSRelay-C

Though the Relay/Power Board is not required, it is a convenience and can reduce the chance of miswiring during the installation. The relay board provides a central place for all of the required relays, fuse protection, and external wiring for the MegaSquirt ECU. If you are installing MegaSquirt in a previously fuel injected engine you may be able to reuse all of your existing relays. If you are fuel injecting a previously carbureted engine you will need to install relays for the main ECU power, Fuel Pump, and FIdle circuit. You can do this manually or you can use the Relay Board to simplify this process.

Comes with DB-37 connector to be used to build your relay cable, and the “half-case” shown in the picture. The parts on the relay board are capable of standing up to an under hood environment.

Uses standard ‘mini-ATO’ style fuses. (not included) Recommended fuse values:

  • 20 Amp main fuse
  • 10 Amp fuel pump fuse
  • 5 Amp fuses for INJ1 and INJ2 with a 4 cylinder engine, 7.5 Amps with an 8 cylinder.

You may need to change these values based on your needs. These are good starting values.

Make sure to check out our Relay Cable for connecting the Relay Board to your MegaSquirt ECU, and our Wire Bundle which comes in handy for wiring up all of the sensors/injectors/etc to the Relay Board.

For a tech/how-to video for installing your MegaSquirt Relay Cable into your car, check out our Tech & How-To Videos Page.

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What are the four holes next to the fast idle relay?

  • These bring out the connections from DB37 pins 3 through 6 and allow you to connect wire leads to these. Our latest relay cable includes these connections populated.

How do I connect wires to the three large power connections?

  • You may solder wires to these connections, or use a ring terminal and through bolt.

Is there a cover available for the relay board?

  • The relay board is designed to use a half case without a cover.

What wiring do I use with the relay board?

  • Use our Relay Cable to connect the Relay Board to the MegaSquirt, and the Wire Bundle to connect the relay board to the engine.

How do I use the relay board with an MS3X?

  • The outputs that go to the main board are routed through the relay cable, while connections to the MS3X use a separate connector that bypasses the relay board.

Where is this board assembled?

  • We assemble the Relay Board in Gainesville, Georgia, USA.

Questions & Answers

    I notice that there are 2 power in lines for the relay board. Why? What does each do specifically? You have a "switched" input and a +12v input. Why the need for two?
  1. 0 votes
    Q I notice that there are 2 power in lines for the relay board. Why? What does each do specifically...... Read more
    Asked by K Jones

    The +12V input is a full time fused power connection. It connects directly to the battery through a suitably large fuse. The switched 12 volt input is for key-on power. It uses a small amount of current to activate the main relay and power up the remaining components on the board, so you're not trying to pull the entire current requirement for your EFI system through your ignition switch.

    Please see the first article of our Chevy Nova project series for more details on how to wire up this relay board.

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