Fuel Sender-Ground ?

Hi all,
Finishing my fuel tanks and installing the senders. Is it necessary to supply a seperate ground wire or do they get sufficient ground thru the attachment screws ? Even with the Pro Seal ? Are the cork gaskets needed if the covers are Pro Sealed on ? Same for the sender gaskets ?
Also, the plans say to check the resistance on the senders...is there an adjustment ?
Thanks
Mike

mvs163 said:

Hi all,
Finishing my fuel tanks and installing the senders. Is it necessary to supply a seperate ground wire or do they get sufficient ground thru the attachment screws ? Even with the Pro Seal ? Are the cork gaskets needed if the covers are Pro Sealed on ? Same for the sender gaskets ?
Also, the plans say to check the resistance on the senders...is there an adjustment ?

Click to expand...

I have no gaskets, all pro-sealed and no leaks. There is no ground wire either. You can connect your floats to the fuel gauge (would need power) or an ohm meter to make sure they read correctly.

L.Adamson --- RV6A

A short ground...

mvs163 said:

Hi all,
Finishing my fuel tanks and installing the senders. Is it necessary to supply a seperate ground wire or do they get sufficient ground thru the attachment screws ? Even with the Pro Seal ? Are the cork gaskets needed if the covers are Pro Sealed on ? Same for the sender gaskets ?
Also, the plans say to check the resistance on the senders...is there an adjustment ?
Thanks
Mike

Click to expand...

...link to one of the sender holding screws would do no harm....

There is a minor adjustment available by bending the stops that control the arm swing. But if you have an electronic gauge, the precise resistance value makes no difference, the gauge will calibrate to what the sender puts out.

If you are using a non-calibrateable (new word......) gauge, the sender should be 33 and 240 ohms at the limits - 240 ohms is the EMPTY value.

Great timing

My last squawk to tackle. This thread has good timing.

The Dynon is not acknowledging the senders (both tanks). I am going to have to pull the wing root fairing off and check the resistance. Tanks are about 1/3 full and a rock should make the resistance change. I'm afraid I'm not getting a good ground return.

My question, If I have to remove a screw to install a ground, which one, and what about the reseal?

Sometimes the sender doesn't have a good ground through the sender body because a film of proseal. One way to deal with it is put an internal tooth lock washer under one of the screws during installation of the sender and cover plate to help make sure there is a good ground through to the wing structure.

If a gauge is not working the first thing to check is for good continuity (zero ohms) between the sender body and airframe ground.

Webb said:

My last squawk to tackle. This thread has good timing.

The Dynon is not acknowledging the senders (both tanks). I am going to have to pull the wing root fairing off and check the resistance. Tanks are about 1/3 full and a rock should make the resistance change. I'm afraid I'm not getting a good ground return.

My question, If I have to remove a screw to install a ground, which one, and what about the reseal?

Click to expand...

I used a STAR WASHER with a LUG that had a wire solder to it under one allen screw of each sender. After 11-years and over 2,160 flying hours no problem with fuel indication.

If you take one screw out and add a ground lug with NEW ProSeal, there is a 90% chance that it will not leak. Make sure that everything is CLEAN when you put it back together with ProSeal.

Before adding a ground, test the sender with a ground connection to it. Also you can use an ohm meter to go from the sender screw to the sender case.

The float type senders are rated at 0 ohms to 300 ohms. In actual use, it is more like 4 ohms to 280 ohms. I forget if low resistance is full or empty. You can calibrate the senders this way before installation by bending the stop tabs so that both left and right read the same at min and max. That is how I did it back in the late '80 or early '90 when I was building.

See post #3...

RV6_flyer said:

...

The float type senders are rated at 0 ohms to 300 ohms. In actual use, it is more like 4 ohms to 280 ohms. I forget if low resistance is full or empty. You can calibrate the senders this way before installation by bending the stop tabs so that both left and right read the same at min and max. That is how I did it back in the late '80 or early '90 when I was building.

Click to expand...

...for the real SW numbers....

Calibrate the Dynon first

Webb said:

The Dynon is not acknowledging the senders (both tanks). I am going to have to pull the wing root fairing off and check the resistance. Tanks are about 1/3 full and a rock should make the resistance change.

Click to expand...

Did you calibrate the Dynon for the fuel tanks? If the Dynon is not calibrated it will not acknowledge any level of fuel in the tank.

When I was setting up my Blue Mountain EFIS, it would not read the senders. I was told that common ground was not effective; perhaps the same could be true of other digital systems like the Dynon. In any case, I ended up using nylon shoulder washers under the screws for the sender plate to isolate it from common ground and then running a return wire (I used a ring terminal that fit under one of the shoulder washers so it contacted the sender plate but not the screw) back to the Blue Mountain unit. Worked like a charm.

Couldn't calibrate

Lycosaurus said:

Did you calibrate the Dynon for the fuel tanks? If the Dynon is not calibrated it will not acknowledge any level of fuel in the tank.

Click to expand...

Dynon did not acknowledge the sending unit when trying to calibrate. On either tank. I'm almost sure it is failure to have a ground return for the circuit. I will have to order one of the miniature proseal kits from Vans. Heck - what's another 10 bucks now.

I lost the bet

Webb said:

Dynon did not acknowledge the sending unit when trying to calibrate. On either tank. I'm almost sure it is failure to have a ground return for the circuit. I will have to order one of the miniature proseal kits from Vans. Heck - what's another 10 bucks now.

Click to expand...

Would have lost that bet.

Took the wing root fairing off one side. Had a ground return on the volt ohm meter. Also rocked the wing and the resistance changed. Then called Dynon. They suggested to check to make sure that you don't have left and right leads confused and that is why they won't calibrate or recognize the sender since you are looking at the wrong tank when trying to do the calibration. Also, see if there is 5 volts present. Makes sense.

If that doesn't work, check the pins next on the 25 pin connector.

Mystery still at large.