## EGT Circuit Error 

This error is found by using the EGT and comparing the reading of the aircraft EGT indicator with the analyzer temperature reading. [Figure 10-78]  The analyzer and aircraft temperature readings are then compared. 

## Resistance of Circuit Out of Tolerance 

The engine thermocouple circuit resistance is a very important adjustment since a high-resistance condition gives a low indication on the aircraft EGT indicator. This condition is dangerous, because the engine is operating with excess temperature, but the high resistance makes the indicator read low. It is important to check and correct this condition. 

## Shorts to Ground/Shorts Between Leads 

These errors are found by doing the insulation check using an ohmmeter. Resistance values from zero to 550,000 ohms can be read on the insulation check ohmmeter by selecting the proper range. 

## Troubleshooting Aircraft Tachometer System 

A function of the rpm check is troubleshooting the aircraft tachometer system. The rpm check circuit in the analyzer is used to read engine speed during engine run-up with an accuracy of ±0.1 percent. The connections for the rpm check are the instrument cable and aircraft tachometer system lead to the tachometer indicator. After the connections have been made between the analyzer rpm check circuit and the aircraft tachometer circuit, the two circuits, now classed as one, are a parallel circuit. The engine is then run-up as prescribed in applicable technical instructions. Both systems can be read simultaneously. 

If the difference between the readings of the aircraft tachometer indicator and the analyzer rpm check circuit exceeds the tolerance prescribed in applicable technical instructions, the engine must be stopped, and the trouble located and corrected. 

