Aircraft Instruments: Knowing how to handle is as critical as how to repair

Fuel Probes
The majority of problems inherent with probes are caused by contamination and corrosion internally and particularly on the connector pins. You can save yourself a trip to the shipping department and possibly your customer some money by making certain the connectors are clean and making good contact.

Tachometers
1. Certain prop and percent types "click and clack" during start-up. If you hear this, it is generally not a problem — it is merely the start mechanism.
2. Electronic tachometers are much more sophisticated and different in your techniques for troubleshooting. Due to the fact the unit has IC's that control its operation, they should not be checked with a standard multimeter.
3. Tachometers that have a synchroscope function usually have problems with the jewel bearings wearing on the shaft; thereby, causing the synchroscope to move sluggishly or not at all.

These points regarding the "care and feeding" of aviation instruments have hopefully provided some insight that will help prolong your instrument and possibly be less costly to you.