Fire Com 110 - TROUBLESHOOTING; Initial Troubleshooting Checks; Intermittent Crackling Issues; Alternator Whine and Noise Reduction

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TROUBLESHOOTING
If the radio interface system does not operate as expected, check the following items:
• Check for power at the unit and confirm that the fuse is not blown or the circuit breaker is not tripped.
• Confirm that a dedicated ground is used for the interface power and not a chassis ground.
• Check for corrosion on headset plug.
• Check that the headset is plugged in all the way.
• Check headset controls.
If these steps do not correct the problem, review the chart below for symptoms and recommendations.
SYMPTOM RECOMMENDED SOLUTION
Intermittent crackling in headset • Check the headset plug. Make sure it is clean for good electrical
speakers contact.
• Check wire connections at the headset module.
• Check wire connections at the radio interface unit.
• Check the CA cable and RJ-12 connectors.
Tip: Determine if the problem is with the headset or the system by
plugging a different headset (if available) into the headset module
and retesting.
Alternator whine and other • Connect both the radio interface and radio to the cleanest power
source distracting noises source possible, without sirens, strobes, flashers, and motors (i.e.
wipers, heater, etc.).
• Check the power and ground connections for both the radio inter-
face and the radio. Make sure they are clean and tight.
• Ensure that power and ground wires for the radio and radio interface
are no smaller than 18 AWG.
• Check MR cable for proper wiring connections.
• Make sure that all battery connections are clean and free from dirt
and corrosion.
• Use separate noise filters on radio and/or radio interface power as
needed.
• Use a robust common ground for both the radio and the radio
interface.
Tip: Check the power to the unit for an AC signal. There should be
less than 300mVAC present on power lines
No sound in headset speakers • Check the volume control on the headset.
• Confirm the radio is operating properly.
• Check the headset plug. Make sure it is clean for the best electrical
contact.
• Confirm that the radio interface has adequate power.
• Check wire connections at the headset module.
• Check the MR cable between the radio and interface unit. Make
sure the screws on the 9-pin D-sub connector are tight. See
Appendix A for wiring.
• Check the CA cable and RJ-12 connector installation.
Tip: Determine if the problem is with the headset or the system by
plugging a different headset (if available) into the headset module
and retesting.