LMU-3640 Installation Guide

LMU-3640 Installation Guide

The LMU-3640 package comes with:

  • The LMU-3640 with internal antennas.
  • A 24-pin power and I/O cable with Red, White and Black wires for power and ignition
  • An optional 16-pin vehicle diagnostic cable

Vehicle Placement of LMU-3640

  • The LMU-3640 is not water resistant and must be installed inside the cab where it can stay dry.
  • Place the unit where it will see as much sky as possible.
  • Do not place under metal that will obstruct the view of the sky
    • GPS signals are very low power and any metal blockage can prevent it from getting good positions.
    • The unit can be installed under wood, plastic or glass.
  • For a covert installation, somewhere inside the dash or cab is best if there isn’t metal in the dash.

Connecting Power, Ignition, Ground and vehicle diagnostic

Failure to connect the power lines in the manner described may result in discharge of the vehicle battery or damage to the device.

For best results, it is strongly recommended that the LMU connection be on its own circuit. Connect the power input directly to the vehicle battery if possible and protect the circuit with an inline fuse. If you must connect through the fuse box, use standard commercial wiring practices to create a permanent installation rather than using press-in fuse clips or other temporary measures.

Make sure that the diagnostic connector and the LMU-3640 power cables are connected to the same voltage power sources. If using a 24 volt system, both should be powered with 24 volts, or both should be 12 volts, but not a mix.


  1. The ground line (black wire) must be connected to chassis ground.
  2. The power input (red wire) must be connected to a constant (un-switched) +12 VDC or +24 VDC supply; preferably connected directly to the vehicle battery terminal or as close to it as possible. This connection point should be fuse protected to not more than 5 Amps. The included wiring harness has fused red and white lines rated to 3 Amps.
  3. The ignition input (white wire) must be connected to the vehicle ignition or another appropriate key operated line, ensuring that power to the ignition wire is available only when the vehicle ignition is on.
  4. Plug the vehicle diagnostic connector into the vehicle’s diagnostic port.
    • NOTE: The LMU-3640 will get power through the diagnostic connector as well as through the power and ground wires. Even though it will power up when you connect it to the vehicle diagnostic port, you still need to connect it to power, ground and ignition in the next steps.
    • The cable also has a pass-through diagnostic connector so you can also plug in any other diagnostic cables that you might use on the vehicle, or replace the vehicles visible diagnostic port with the one on the wiring harness.



Other Input Wiring

For optional inputs, connect to the following wires and let customer service know to confirm these are enabled:


Input 1 – Blue Wire

Input 2 – Blue/Orange Wire

Input 3 – Violet Wire


They default high (off) and require ground signal to trigger low (on).


If you’re connecting an input to a positive trigger, you’ll need to use an automotive relay to convert to a ground trigger. If you’re wiring multiple vehicles, wire them up so the same input type is always the same input number. For example, always make the PTO input 1 and the hood sensor input 2 across your fleet.

Installation Check List

The following must be checked to declare a successful installation:


  1. Turn ignition on.
  2. Lights on the LMU-3640
    1. The Green light must be on solid (no blinking) to show it has obtained a valid GPS fix.  This means the vehicle will probably have to be outside to get a valid GPS fix.
    2. The Orange light with either be solid (no blinking) to show it has successfully connected to the cellular network or will flash at an irregular interval.
  1. Successfully performed ELD diagnostics using the details in the section below.



  1. No 9 pin diagnostic port in the vehicle, or the vehicle has a 6 pin port, or connector doesn’t fit.
    1. Disconnect the cable from the LMU-3640 and send these back to us. Leave the LMU-3640 installed.
    2. Include details in the installation list about why the cable couldn’t be installed so we can send the correct cables.
  2. No lights on LMU-3640.
    1. Confirm that the LMU-3640 is getting power.
    2. The LMU may be sleeping, so turn ignition on to wake it up.
    3. If the lights don’t turn on with ignition, check that the white ignition wire is getting power when ignition is turned on.
  3. Orange light blinking alternating between slowly and quickly (cellular connection).
    1. Wait at least 5 minutes.
  4. Green light blinking (GPS connection).
    1. Confirm the LMU-3640 is not installed directly under metal.
    2. Move the vehicle outdoors if it’s in a shop or metal building.
    3. Wait at least 15 minutes for the LMU-3640 to get a GPS fix and show solid green.