Troubleshooting Avionics Problems
NOTE:
As simple as these steps are, do not attempt any of
them unless you are absolutely sure you know what you are doing. Even
simply removing a panel mounted unit can result in damage if not done
properly. Many procedures require that you have the proper FAA rating. American Avionics
CANNOT be held responsible for any damage if you perform any procedure for which you aren't qualified to do. If there is any doubt, please call our service department first.
The Basics
Check for connection problems - This is probably the single most universal problem that occurs in an aircraft environment. Check plugs and connectors for security and corrosion. Remove rack mounted equipment and re-insert them to insure you have a good connection. Do NOT clean connectors with harsh solvents, or degreasers that can leave surfaces bare and un- protected. Use only approved electrical contact cleaners that leave behind an anti-oxidant. Cleaners that leave "no residue" will leave contacts free to oxidize and corrode.
Check for blown fuses or Circuit Breakers - Fuses can eventually blow with age and vibration. Circuit Breakers can become weak and intermittent with time, cycling, and overloads. Press or wiggle them-even cycle them- to determine if they are intermittent. Replace them if they are. If a circuit breaker pops instantly and after it has cooled, you may have a serious short circuit. A circuit breaker typically requires that at least twice the rated amount of current is flowing through it for it to pop instantly. IE, a 5amp breaker under a 6amp overload will take about 1.5 minutes to pop. It should pop instantly with 10 amps or more. A few instances of this, and it should be replaced after the overload is repaired.
Check Antennas For Wear or Damage - Check plastic and fiberglass antennas for abrasion, cracks and holes that can let moisture in. Also check that the sealant around the bases of antennas is sound. A rubber gasket is not typically going to do its' job after years of flying. Also if your DME and Transponder antennas are the 4 inch steel rod type, ensure that they are not bent, greasy, or loose. These small rod antennas are notorious for getting broken inside the base when the airplane is washed and the rod gets bumped. A light pull, straight out, will usually indicate this condition if the rod pulls right out of the base and into your hand.