Troubleshooting the Horn on a Finch II Display

The horn circuit on a Finch II Display is easy to troubleshoot. See the TPM 010 Finch II Installation and Operation Manual and the diagrams below for guidance. This article covers all versions of the Finch II display.

The troubleshooting steps are slightly different for when the horn was working well and then quit or it is newly installed. The in-service failure is easier to troubleshoot. It was working before and then something happened to it. Installation problems may require more in-depth troubleshooting.

See the diagrams below for guidance.

Figure 1 is a view of the Finch II’s circuit board horn connections, test button and fuse.

Figure 2 is the basic electrical wiring diagram.

Figure 3 is the horn wiring.

Figure 4 is the basic installation diagram.

Troubleshooting the In-Service Problem

The horn was working and then it quit. The problem is logical and so is the solution. The most common reason for the horn to quit working is a loose or corroded connection or cut wire. Next is a blown fuse. Remember that when a fuse blows, you are looking for a wiring problem that has shorted the horn power to ground, not a loose wire. Next is a defective horn.

The following troubleshooting steps will help lead to the problem.

To test for voltage, place the test light clip or the Voltmeter negative probe on the ground. This is an unpainted metal part connected to the frame of the vehicle. You may also use the GND IN terminal on the circuit board. See Figures 1 and 2. Probe for voltage with the test light or Voltmeter positive probe. The test light will illuminate and the Voltmeter will indicate normal vehicle voltage.

To test for ground, place the test light clip or Voltmeter positive probe on the PWR IN terminal. See Figures 1 and 2. Probe for ground with the test light or voltmeter negative probe. The test light will illuminate and the Voltmeter will indicate normal vehicle voltage.

1. Ensure that all alarms are inactive.
2. Press the Horn Relay Test button, see Figure 1, to determine if the horn is working.
   1. If the horn works, you are looking for an intermittent problem. It’s usually a wire that’s barely making a connection.
   2. If the horn remains silent
      1. Check the horn fuse. See Figure 1. If the fuse is blown, replace it and continue to inspect the wiring.
      2. If the fuse is OK, continue troubleshooting.
3. Check the horn wiring according to Figures 2 and 3. You are looking for a loose or corroded connection or a cut wire.
   1. If you find the wiring problem, repair it and retest using the Horn Relay Test button.
      1. Note that the horn is polarity-sensitive with + and – terminals. Observe the polarity according to Figure 2.
4. If you didn’t find a wiring problem the next step is to use a test light or Voltmeter to check for power or ground at each point in the horn circuit. See Figures 2 and 3.
   1. Check for voltage at Relay PWR terminal-4.
   2. Check for voltage at Relay 4 COM terminal-3
   3. Check for voltage at Relay 4 NO terminal-1. Press the Horn Relay Test button to activate the relay.
   4. Check for voltage at the horn + terminal. Press the Horn Rely Test button to activate the relay.
   5. Check for ground at the horn – terminal.
   6. Check for ground at the Relay GND terminal-5 
      
      Failure of test steps 4a, b, c and f indicates a defective Finch II display.
5. If you still haven’t found the problem, the cause is a defective horn.

Troubleshooting an Installation Problem

This is more challenging. You are looking for something out of place. It may be a missing wire, a connection to the wrong terminal or a blown fuse due to miswiring. The best approach is to start with the first step of installing the horn. Confirm it was done correctly. Continue checking each step until you find the error. If you discover that the horn power was shorted to ground, check the fuse and replace it if needed.

Use the Horn Relay Test button to test the horn as you troubleshoot.

Consider the following:

1. The horn may or may not be a self-grounding style. Bolt the self-grounding horn to an unpainted metal part connected to the vehicle frame.
2. The horn relay may not be configured correctly. Check the relay configuration using SensorLink and a programming kit.
3. Ensure all fuses are in place and especially check the horn fuse to confirm it hasn’t blown.
   

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Figure 1, Finch II Circuit Board

Figure 2, Finch II Basic Electrical Wiring Diagram

Figure 3, Finch II Horn Wiring

Figure 4, Basic Installation Diagram