Hardwiring the MXT115/MXT275

Tools & Materials Needed

• Wire strippers / crimpers
• Multimeter (for checking power/ground)
• Add-a-fuse kit (recommended for fuse box wiring)
• 15A inline fuse holder (if not already included in the radio power cord)
• Crimp connectors or solder/heat shrink
• Zip ties / cable loom (for wire management)
• Electrical tape

Step 1: Plan Your Install

1. Choose the radio location
   • The MXT275 has a detachable faceplate mic, so you can hide the main unit (glove box, under dash, center console) and mount the mic/controls where reachable.
2. Choose the power source
   • Option 1: Direct to vehicle fuse box using an add-a-fuse kit.
   • Option 2: Direct to battery (with fused positive line).
   • Option 3: Cigarette lighter plug (stock cord), but not true hardwire.
3. Choose a grounding point
   • Use a solid, bare metal chassis ground close to where you mount the radio.

Step 2: Identify Power Wires

The MXT275 power cord has two wires:

• Red = +12V (positive)
• Black = Ground (negative)

The radio requires a 12V DC supply, fused at 2A.

Step 3: Hardwiring Options

Option A: Fuse Box 

1. Locate your fuse box inside the cab.
2. Pick a circuit:
   • Switched power (radio turns on/off with ignition) → example: radio, wipers, or accessory fuse.
   • Constant power (radio always has power, must be turned off manually) → example: dome light or battery fuse.
3. Install an add-a-fuse kit:
   • Insert into the chosen fuse slot.
   • Plug original fuse into lower slot, and a new 2A fuse for the radio in the upper slot.
4. Connect the red wire from the MXT275 harness to the add-a-fuse lead.
5. Secure the black wire to a clean chassis ground (bolt to bare metal).

Option B: Direct to Battery

1. Run wires through the firewall (use a grommet).
2. Connect the red wire directly to the +12V battery terminal.
   • Insert a 2A inline fuse holder within 6–8 inches of the battery connection.
3. Connect the black wire to the negative battery terminal or a chassis ground.
4. Secure wires with loom or zip ties along the run.

Step 4: Antenna Connection

1. Mount your antenna (mag-mount, NMO roof, or fender mount).
2. Route the coax cable into the cab (avoid sharp bends & hot engine parts).
3. Screw the antenna coax into the back of the MXT275 main unit.
4. Run an SWR check for best performance.

Step 5: Final Checks

• Use a multimeter to verify 12V at the red wire and solid ground on black wire.
• Power on the radio.
• Key up briefly (check TX light) and listen for received audio.
• Tidy wiring with loom and zip ties.

Safety Tips

• Never connect red wire without a fuse in line.
• Don’t ground to painted or rusty metal—scrape to bare metal.
• Keep wires away from pedals, sharp edges, or moving parts.