Gas gauges

[art.pileggi]

I just got the plane back from annual, I updated the software to the 04/05/13 version (AFS-5600).

My left tank has about 8 gallons and my right tank about 13 (full tanks are 13.1). The calbration settings on both tanks is 924 for full tanks. The current actual readings vary rapidly between 1027 and 1150 on both tanks even though on is 5 gallons lower than the other.

Any suggestions?

[Rob Hickman]

We have not had any other reports of fuel tank reading problems with the new software. I would suspect something got messed up while doing the annual.

do you have float or capacitance tank sensors?

[art.pileggi]

I went back to the plane, reloaded the version from 03/03, it didn't help. I reloaded the current software. Serves me right for changing too many things at once.

Today with no wind and the engine not running the right tank was varying from 900 to 1400 (greater variation than Sunday). The left tank was varying from 500 to 1000. Since the difference in ranges is in line with the actual amount in the tank some signal is being received from the tanks.

I don't know the sensor type and after looking at the tank calibration screen I can't see anything that would tell me.

Something happened during the annual. It is my understanding from the manual that if the wires were not connected the gauage would not read anything. It seems unlikely that both tank gauges failed at the same time. So I am look for something to tell the mechanic to check. Any suggestions?

Art

[Rob Hickman]

Are any of the other gauges fluctuating?

Check and see if the voltage is changing on the tank sensor with a volt meter.

Did they change anything else during the annual?

[art.pileggi]

Finally got to the plane again.

With the sensor plugged into the wire (I assume the wire goes to the AF5600), the voltage is varying very quickly between 900 and 1200 mv (I now am assuming that the AD reading on the 5600 is in millivolts). If I disconnect the sensor from the wire, the wire voltage is 3.6 volts solid, and the sensor is 25.6 mv. The AD value on the 5600 is 3610 (also solid).

When I put a ohm meter on the sensor it is varying between about 900 and 1200 ohms.

It certainly makes me suspect the sensor, but I am at a loss as to why both sensors would fail right after the annual. Any ideas?

Durning the annual they rewired the alternator and generator warning lights. They fixed a broken wire in the alternator harnes. The replaced the main battery. They rewired the trickle charge line to the TRW battery backup. They did not delibrately do anything to the AF5600 or any other avionics system (except the ELT which they checked).