Description
Reliable High-Power Controlfor when regular switches won’t work
FUNCTIONAL
Your high-power solution. When regular switches can’t handle high-current loads, adding relays can become a complicated and messy project. That’s where MGI steps in — our fused relay boxes provide centralized control and protection with minimal wiring involved.
EASY INSTALLATION
Wiring is made easy. Each bosch relay box comes with a red main feeder cable and labeled screw terminals. Use the Installation Manual and wiring diagrams to help connect your power source, switches, and loads. It’s that easy.
RELIABLE
Quality is Guaranteed. Our Bosch relay boxes are routinely tested, with relays rated 40A at 12 volts to ensure optimal reliability come race time. Produced only with GXL high temperature wire, with no-nonsense screw terminal strips for reliable input and output wiring.
Bosch Style Relay Box Featuresuse our interactive builder to customize your multi relay control box
Choose the Number of Relays
We understand that space is a valuable commodity in your rebuild or showcar. That’s why we’ve designed automotive relay boxes with your choice of 4, 6, or 8 relays. Each relay box has at least one 5-pin relay that can be wired for normally closed operation if needed.
Choose Your Fuses
Each MGI relay box comes with fuses tailored to your specific loads. Don’t know what fuse sizes you need? Don’t worry — MGI uses an industry standard, tried-and-true formula to provide recommended fuses sizes for your individual loads. A similar approach is used to calculate the main fuse size.
- Simply enter your current load for each relay into the calculator
- and indicate whether it is a motor load.
With this information, MGI will supply you with appropriate fuses unless otherwise selected.
Relay Box Wiring Diagramshow to install 4, 6, and 8 relay boxes
STEP 1
Battery Power
Connect the red main feeder conductor to the car starter’s battery power terminal. Then, install the supplied main fuse and holder in the main feeder conductor between the starter and the power stud found inside the panel.
STEP 2
Switches & Grounds
Connect the black ground wire (with red ring terminal) to the auto chassis. Then, connect the control circuit wire(s) to your switch inputs, with outputs connected to the appropriate screw terminals.
STEP 3
Outgoing loads
Connect your loads to the appropriate screw terminals. Ground your loads. See the 4, 6, and 8 relay box diagrams above. In addition to regular N.O. circuits for each relay, the RCP4 has 1 optional N.C. circuit, the RCP6 has 2 optional N.C. circuits, and the RCP8 has 3 optional N.C. circuits.
WHAT’S INCLUDEDwhat comes with every SPDT Bosch relay panel kit
- Aluminum frame and your
choice of 4, 6, or 8 built-in relays
- 40 Amp SPDT relays
- Optional N.C. circuits
- Relay-corresponding LEDs for visual troubleshooting
- When relay closes, LED turns on
- Integrated LED blade fuses (+ spares)
- ATC / ATO style blade fuse with LED light that glows when blown
- Available in sizes 5 to 40A
- 5A LED control circuit fuse (+ spare)
- Main fuse & fuse holder
- Mini ANL bolt-down fuse
- Available in sizes up to 150A
- 5′ main feeder conductor
- Available in sizes up to #2 AWG
- ½” strain relief cable gland connector(s)
FREQUENTLY ASKED QUESTIONSAnswers to Popular questions
Why buy a fuse & relay box?
When rebuilding, restoring, or refurbishing your vehicle, you’re bound to need electric pumps, fans, spotlights and more. These high-current devices will damage regular ignition key switches or low-current switch panels — however, an electromagnetic switching relay box will give you the safe and reliable control you need.
Can this relay box operate “normally closed” devices?
Yes! Our unique SPDT Bosch style relay boxes can power devices that are normally closed.
- RCP4 has one N.C. output (terminal #12)
- RCP6 has two N.C. outputs (terminals #9 & #10)
- RCP8 has three N.C. outputs (terminals #13, #21 & #25)
WIRING EXAMPLESsome popular relay panel projects
Nitrous Trans-Brake Circuit
A nitrous trans-brake system is a great example of SPDT wiring that uses both the N.C. and N.O. relay box circuits.
See the RCPX Nitrous Trans-Brake Wiring Diagram. In this case, the N.C. nitrous circuit (with its own arming switch) is active only when the trans-brake switch is open.
Switches
Switch Panels
Fuse Boxes
Wire Loom
Battery Cable
Primary Wire
Blade Fuses
MIDI Fuses
Crimp Terminals
Raym (store manager) –
high quality and works well. Not cheap plastic like other relay boxes.
Dan_H (store manager) –
Good but wish it came with a waterproof box for my buggy in the mud.
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