ATA 28-43, Fuel Tank Temp

There is one resistor based fuel temp bulb installed in the left wing tank. The higher the resistance, the higher the temperature indication.

We had an aircraft reading -40C. The temp bulb resistance measured 80 ohms. (Actual outside temp was just above freezing.)

When compared to a functioning aircraft showing a temp of 1C, the temp bulb read 93 ohms.



Double plug indicators: P3900 pins 8 and 9.
Triple plug indicators: P3896 pins 12 and 13 (13 being ground). P3896 is the middle smaller plug.



AMM Task 28-43-00-715-018-002 shows low end resistance (-30C) as 80 ohms and high end resistance (60C) as 112 ohms.

Replacement probe. Two red wires for indication. Two white wires for data recorder (I found the majority of aircraft did not use the white wires).



Left wing panel, just outboard of gear.



Probe housing tucked behind some hydraulic lines. The probe slips into a dry bay, not into the actual tank.

Always thought it was inside the tank, wow thanks Mark!