Electrical Power Loss Troubleshooting for TD100 Systems

Your best tool for troubleshooting low or no power to the TD100 system is your eyes. The Finch II Display provides an error code for low voltage. No lights on the Finch II Display also tells a story. The Rack Control Module (RCM) indicates when the voltage from the display is low.

Are the trailer lights dim? That indicates a larger vehicle electrical problem or a weak battery in the trailer lights tester.

See Figure 1 for Voltage measurement locations.

Troubleshooting Indications

• Finch II error code E0802 indicates low voltage to the display.
• Finch II 3V3 power LED on the circuit board when dark indicates no power or internal failure.
• RCM power indicator blinks for low voltage.
• Lights and 7-segment display on the Finch II Display are dark. This indicates no power or internal failure.
• Trailer or truck lights and other equipment operation. Are the lights dim? Is the ABS blinking a code for low voltage? This indicates a vehicle electrical problem.
• Voltage measurements using a DMM. Refer to the required minimum voltages for normal TD100 system operation listed below.

The Finch II Display may also be defective. The most common cause of an E0802 error is external wiring. Measure the voltage at the Finch II Display PWR IN and GND IN terminals. It must be well over 9VDC and stable for normal operation. Low voltage at this point indicates external vehicle wiring issues. An acceptable voltage here indicates a possible internal Finch II Display problem. 

Troubleshooting Tools

Required Tools:

• Your eyes for visual inspection

Optional or Used as Needed:

• Digital Multimeter (DMM) to measure the voltage.
• Electrical test light to indicate the presence and stability of the voltage.
• Bright flashlight or work light to inspect the wiring and connections.

 
Causes of an In-Service Failure

When troubleshooting for power problems, consider that the most common in-service failure is damaged wiring or corrosion. See the points below for guidance.

• Low truck battery charge
• Poor electrical connections. Inspect for the following:
  • Worn or cut wires
  • Worn connector pins
  • Corrosion on terminals and connector pins
  • Loose connection on terminals
  • J560 sockets and cable to the trailer issues

Causes Due to Testing

When troubleshooting or testing, your test equipment may be causing the problem. It may be the power supply at fault and not the trailer wiring. Consider the points below.

• Low battery voltage in trailer lights tester
• Using an underpowered power supply for testing
• Do not use a battery charger for testing

 
Truck or Trailer Electrical Troubleshooting

1. If the voltage at the Finch II PWR IN and GND IN terminals is at least 9VDC and stable, the problem is possibly but not always with the TD100 system. Troubleshoot the TD100 system. See the TPM 010 Finch II Installation and Operation Manual and TPM 057 TD100 Installation and Operation Manual for troubleshooting guidance.
   
   Note that many of the other electrical systems may not work properly with a reduced voltage. Measure the battery voltage at the truck’s battery terminals. With the engine running, it should be about 14.5VDC. If you measure 14.5VDC at the battery and 9VDC at the Finch II power terminals, there is a serious problem with the vehicle’s electrical wiring. Resolve this issue first.
   
   
2. Voltage measurements using a DMM may not detect an electrical problem. DMMs are good for accurately measuring voltage, current and resistance. They are not good at detecting unstable power. The power fluctuations can happen quicker than the DMM responds to measurements. Keep this in mind when troubleshooting.
   
    A simple lightbulb test light may be a better tool for detecting unstable power. An incandescent lightbulb visibly flickers with unstable voltage. The degree of brightness and flickering also indicates the severity of the problem.
   
   
3. If the voltage at the Finch II Display is less than 9VDC or is unsteady, the problem is with vehicle wiring or the battery. Troubleshoot the vehicle's electrical system.
   
   Check the following:

• Check vehicle power fuses if there is no voltage at the Finch II Display PWR IN terminals. Continue to check for a wiring problem if the fuses are OK. If a fuse has been replaced, continue to test the TD100 system. There’s a reason why fuses blow to protect an electrical circuit.
  
  
• Check the power and ground wiring from the Finch II Display to where it is connected to the vehicle battery power. You are looking for worn or cut wires, corroded or loose terminals and worn connectors. Check the wiring from the Finch II Display through the following components:
  • Junction boxes
  • Fuses and fuse holders
  • TD100 system power control such as a Hobbs switch on the brake air line
  • Any interlocks that interrupt power to the TD100 system
  • J560 sockets and cable between the truck and trailer or B-Train units
    
    
• Pay attention to where electrical ground connections are made to the vehicle chassis. The connections must be made to bare, unpainted metal and be corrosion-free.
  
  
• Measure the truck battery voltage. The TD100 system won’t work if the battery charge is too low for normal operation.
  
  
• Measure the trailer lights tester battery if it is used to power the TD100 system. The TD100 system won’t work if the battery charge is too low for normal operation.
  
  
• Ensure that a battery charger is not connected to the TD100 system. The TD100 system will not operate normally when powered by a battery charger.

Battery Voltage Specifications

Power-related problems are all due to low truck battery voltage or the wiring that carries the electrical power to the TD100 system through the Finch II Display.

System voltage is measured with the TD100 system fully energized along with all the normal accessories such as the spill prevention system and lights. The battery and wiring must maintain a minimum and stable voltage for the TD100 system to operate normally. Note if there are any other indications such as dim trailer lights. These symptoms point to a larger vehicle electrical problem.

The following normal voltages are measured inside the Finch II Display.

• Engine off, about 12VDC to 13VDC at the PWR IN terminals
• Engine running, about 13VDC to 14VDC at the PWR IN terminals
• Minimum voltage to Finch II Display, 9VDC and stable
• Minimum voltage to TD100 Transmitter, 8VDC and stable
• Minimum voltage to the RCM, 8VDC and stable
• Finch II voltage drop from PWR IN terminals to transmitter power is about 1VDC
  • 9VDC minimum into the display for normal TD100 Transmitter and RCM operation
• Finch II voltage drop from PWR IN terminals to Relay Power terminals
  • No voltage drop, same as PWR IN.

Figure 1, Voltage Measurement Locations

The locations in Figure 1 are where the DMM probes are placed for voltage measurements inside the Finch II Display. Note that the terminals are filled with plugs and wiring. They have been removed from this drawing for clarity.

1. Black (-) probe on GND IN terminal.
2. Red (+) probe on the PWR IN terminal to measure the voltage into the display from the vehicle’s battery power system. It must be at least 9.1VDC and stable.
3. Keep Black (-) probe on GND IN terminal, Red (+) probe on the RELAY PWR terminal to measure voltage to the relay-controlled optional horn, lights and spill prevention system. It must be the same as the voltage at the PWR IN terminal.
4. Keep Black (-) probe on GND IN terminal, Red (+) probe on the TD80 #1 PWR terminal to measure voltage to the TD80 or TD100 Transmitters. It must be at least 8VDC and stable.