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AFS3500

Mattmountain

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Hello
I have a question about intermittent fuel flow on an AFS3500. Basically anytime it is warmer than about -5C there is no fuel flow data. We have an O-360 A1A in an RV-7a. We have changed out the red cube fuel transducer with no change. Wires have been inspected thoughtout the system to the 3500 harness and it all seems to be in order. The 3500 is running the most up to date software update. When the fuel flow is working it seems to be very accurate against lycoming numbers and compared to another -7a with the same set-up.

Although probably not related the fuel level for one of the tanks always shows empty, except when the weather is very cold, below -15C, and then it reads correctly.

Has anyone else experienced anything like this ?

Thanks
Matt
 
On a 4500 rather than 3500

On a recent flight I noticed for the first time a fuel flow of zero. Like you I changed out the red cube, tested all the wires and finally checked the EFIS output. I contacted AFS, and they told me that they pin out power to the red cube at 5V (the red wire) and this has worked well for them. Electronics International, it turns out, specs out the red cube at 8-30 V. AFS suggested I move my power output to my trim power out pin on my harness, which is 10V.

Interestingly, when I did check the white signal wire FROM the EFIS (not from the cube), and rapidly grounding it repeatedly (a test suggested by AFS), the EFIS gauge does register a fuel flow.

Knock on wood, but the switch to a higher voltage seems to have fixed the problem for me. (Although I am still puzzled why it worked for a while for me at 5V, and seems to work for most others at 5V)
 
On a recent flight I noticed for the first time a fuel flow of zero. Like you I changed out the red cube, tested all the wires and finally checked the EFIS output. I contacted AFS, and they told me that they pin out power to the red cube at 5V (the red wire) and this has worked well for them. Electronics International, it turns out, specs out the red cube at 8-30 V. AFS suggested I move my power output to my trim power out pin on my harness, which is 10V.

Interestingly, when I did check the white signal wire FROM the EFIS (not from the cube), and rapidly grounding it repeatedly (a test suggested by AFS), the EFIS gauge does register a fuel flow.

Knock on wood, but the switch to a higher voltage seems to have fixed the problem for me. (Although I am still puzzled why it worked for a while for me at 5V, and seems to work for most others at 5V)

This is interesting. The Dynon systems use 5V also and I haven't seen too many reports like this. Although, the Dynon uses a dedicate power output for the red cube; at least the D120 does. Maybe at those voltages it is sensitive to drain or interference.

Larry
 
For what it is worth, the harness pin for 10V power out from my 4500 was the pin out for flaps pwr, not trim. I typed in error on my response above.
 
Hello
I have a question about intermittent fuel flow on an AFS3500. Basically anytime it is warmer than about -5C there is no fuel flow data. We have an O-360 A1A in an RV-7a. We have changed out the red cube fuel transducer with no change. Wires have been inspected thoughtout the system to the 3500 harness and it all seems to be in order. The 3500 is running the most up to date software update. When the fuel flow is working it seems to be very accurate against lycoming numbers and compared to another -7a with the same set-up.

Although probably not related the fuel level for one of the tanks always shows empty, except when the weather is very cold, below -15C, and then it reads correctly.

Has anyone else experienced anything like this ?

Thanks
Matt


This sounds like a connection problem somewhere, likely in a circuit board. The fact that you have two distinct errors that only appear/disappear in cold temps would indicate that something that is suppose to be touching or not touching at all times is not solidly connected and the thermal expansion rate is causing it to touch/separate at certain temp threshhold. That connection could even be in discrete component like a resistor or capacitor.

Larry
 
Thanks

Thank you to all who replied. Finally got the issues sorted out and surprisingly it was two different issues.
First on fuel flow it was a bad red cube. We put an oscilloscope on the unit and it wasn't showing any signal at all. Rapidly Grounding out the white wire from the Efis did cause it to indicate flow. Changed the unit and flow has worked for approx. 25 flight hours so far.

Fuel level was a different issue and turns out we had to send the unit back to AFS to get that sorted out. They replaced some internal parts and that corrected the tank level issue.

On a side note we did have some additional issues with the Efis, not sure if they were internal to the unit or a grounding issue. AFS replaced most of the internal components and we ran new ground wires. Not sure which actually fixed it but so far everything is working exactly as it should. Just got back to Ottawa from Oshkosh and it was rock solid both ways.

Rob from AFS was awesome to deal with. Great customer service !

Thanks
 
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