Testing Resistive fuel sending units

[litewings]

Have a -0- fuel indication on a a RV8 with standard Vans sending units. Anyone know what the resistance should be from full to empty? Graeter resistance while in the full position or empty position? Hopefully something that can be checked with a ohmmeter.

[BobTurner]

My memory is something like 40 ohms to 300 ohms??? I forget which way is full/empty.

[dynonsupport]

The senders tend to be about 10 to 300 ohms. If it reads a dead short to ground (0 ohms) or above about 500 ohms, you have an issue. They should read lower with higher resistance, so zero fuel sounds like high resistance.

[aturner]

I had a fuel sender that initially did not work because I was too good with the proseal, and it was insulated from the airframe. Solved by adding a star washer under one screw head. Check to see if you have continuity from the sender body to the airframe.

[rvbuilder2002]

Senders supplied by Vans are 30 to 240 ohms

[rvbuilder2002]

Originally Posted by aturner

I had a fuel sender that initially did not work because I was too good with the proseal, and it was insulated from the airframe. Solved by adding a star washer under one screw head. Check to see if you have continuity from the sender body to the airframe.

Andy is correct
This is the most common problem

[litewings]

Thanks for the answers.

[maus92]

I'm not sure what type of sending units the original builder installed in my RV-8. My issue is that the left tank either indicates empty, or some level which appears to be an accurate based on visual inspection/time feeding from tank. There is a single wire that leads from *somewhere behind the tank* then into the fuselage. The right tank looks to be indicating properly. This has always been an issue with the plane since I've owned it, not something that just started. Questions:

How can I tell if this is a capacitance vs. resistive system?
What type of problem does this type of intermittent behavior indicate?
How should I test the system?

Thanks!

CA

[David Paule]

I measured the fuel float sender yesterday for the RV-3B tanks I'm building. This was for the right tank, the left tank isn't quite ready to test yet.

Full was 31 ohms. Empty was 241 ohms.

Dave

[jjconstant]

Be careful tightening the screw for the wire to the gague. It is very easy to overtighten and it will break the wire on the tank side of the sender, resulting in either intermittent problems or zero gallon reading. The only solution then is to remove and either replace the sender or re solder the wire.