Clean-Up Crew: MSD High-Current Solid-State 4 Channel Relay

We’ve all been there before: eagerly awaiting the muscle car’s owner to get out and showcase his new build. They step out while reaching down and release the hood. Your excitement increases. They release the safety latch and begin to lift as the engine bay comes into view.  The engine bay is freshly detailed, spark plug wires are nicely routed and everything looks like a winner. However, the finishing touches are lacking. You quickly notice a string of four 12-volt 30-amp relays and an obscenely large positive power lug haphazardly bolted to the inner fender wall. Each relay has a series of five wires heading all directions from under it joined only by crimped female spade connectors. The positive power lug could be used as a sizing chart for all gauges of wire.  Your excitement dwindles as the engine bay’s wiring leaves something more to be desired.

Thankfully MSD has created a solution to put your muscle car’s electrical department back on track and keep the excitement level amped up! The new high current solid-state relay is a one-stop-shop for all your wires allowing you to ditch the cache of phased out relays. The fear of wiring is relieved as the main positive and main negative is only one wire each. Switched on activation per channel can be handled via ground or 12-volts. The four continuously 35-amp outputs require only a single wire to send power out. Two diagnostic LED bulbs reside directly below each channel’s output and will help determine system on, system off, short circuits, or excessive current draws. Two-bolt mounting enables ease of placement in a variety of locations and orientations.

MSD High-Current Solid-State Relay uses threaded screws to minimize wire slip.

While the setup is simple the usability is where the product shines.  The MSD relay allows you to power up to four items through its four-channel 35-amp outputs for a combined total of 140-amps. Fuel pumps, electric fans, and other large amperage draw items can have two dedicated channels ran in parallel giving it the power they need. To avoid harmful amp spikes you can run a pulse width modulation controller as the activation switch for items such as variable speed fans as long as the duty range is between 50-90% and stays under 150 hertz. The relay operates on a 7-20 volt supply meaning the 16v drag racers will have no issues with overvoltage.  Should a problem arise, the relay block has built-in automatic over-temperature, short circuit, and overload protection, as well as a channel reset. To top it off MSD even has a one-year manufacture warranty!

The MSD solid-State High Current Relay Block is more than just a spaghetti mender for your rat’s nest of wires, it allows you to step into modern electronics without the cost of paying a professional while offering the over-the-top reliability MSD products have. At $174.95 it’s a no-brainer and won’t Hertz the wallet.



  • Operates from 7-Volts to 20-Volt supply
  • 4 Independent Channels, 35 Amps each continuous or 100 Amps for 8 seconds
  • Combined total continuous current rating of 140 amps
  • Channels can be run in parallel for devices requiring more than 35 Amp single-channel rating
  • Clean, easy install with minimum wiring
  • Over-temp, short circuit, and overload protection
  • Diagnostic LED’s and status indicators
  • Multiple mounting options
  • Single wire activation by switching power or ground
  • Available in Red or Black
  • A PWM signal can be used in the Solid-State Relay Module with a maximum frequency of 150 hertz and a duty cycle range from 50% to 90%.


For more information on MSD’s solid-state relay, click here.

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About the author

James Elkins

Born into a household of motorsport lovers, James learned that wrenching takes priority over broken skin and damaged nerves. Passions include fixing previous owners’ mistakes, writing, and driving.
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