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Vans resistive fuel sender inop.

Bill Boyd

Well Known Member
I know I'm not the first person this has bitten - heck, I recall some time in the distant past having to replace one of these in my 6A and what fun that was.

I am calibrating my fuel senders to the Advanced Flight EFIS - very straightforward process: add fuel incrementally and hit "save" to store the value at each selected increment of fuel capacity. The left tank calibration went fine; the right side not so much.

I added five gallons of fuel and determined that the displayed raw data value
(2137) was not changing from the empty tank value. Five gallons more and rocking the wings changed nothing.

Fuel sender wire disconnected and left open: EFIS setup screen showed an AD.VAL of 1. Shorted the wire to ground: AD.VAL of 4094. This is a huge relief as it suggests the wiring is intact, correct, and responsive to resistive inputs. Next, to confirm what I already suspect: wire disconnected from sender terminal, measured resistance of the sender at 0, 5 and 10 gallons in tank: a rock steady 219.4 ohms at all three levels.

So I know I have an inoperative sender. I tried poking around in the drain bung hole with a piece of flexible tubing to see if I could lift the float arm and get a wiggle in the readings but have so far failed. I see a sender replacement in my immediate future (wings on and DAR scheduled for this Saturday) :eek: unless the hive has other ideas.

I purchased the kit with tanks already built and mounted on the wings - assume the float senders are Van's standard issue for the era (2010-2011). At this point I'd be willing to angle-drill a hole in the end of the tank and mount a capacitive sender if it were feasible - the EFIS can be configured independently for either type.

Ideas??
 
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I'll admit to not having tried beating on it yet, not adding more than ten gallons - just rocking the wings laterally. I don't even know if the resistance reading suggests a float arm stuck in the high or low position or somewhere between.

Has anyone removed a float sender in position on the 10? Can it be done without pulling wing or tank? I can see where the aileron torque tube might at least need to come out but perhaps not.

If it will fit through the fuel drain bung hole, I'm ordering an 8.5mm articulating boroscope today as seen on the Savvy Mike Busch Show. :p Should at least let me see if not fix whatever is going on.
 
First guess would be that the bend in the arm is a bit off and the float is hitting the web and stuck in the down position (240 ohms is the full down position -- 33 is full up). Second would be that the metal rod is not fully locked into the plastic arm. If the radius is too large on the bend, the rod won't snap into the locking tab on the plastic arm. There appeared to be numerous things in the vicinity that could cause the float to hang up.

The fact that you get 219 ohms would imply that the sender is functional, but the float/arm is not moving or the float arm is not connected to the sender arm.

I don't believe that I took off the torque tube when installing / testing the sender, but can't be sure. One thing that I did, was to tie a string to the float and ran this string out of one of the screw holes. With the sender pressed flush against the bulkhead, I used the string to insure that the float would go fully up and down without binding on anything.

Larry
 
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Bill,

I installed my float transmitters after installing the wings on my RV-10, and did not have to remove the tanks, so you should be able to remove the non-functioning unit with the wings and tanks in-place.
 
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