[crabandy]

I have the standard resistive float fuel sending units, when doing the fuel capacity calibration It wasn't working right. Seems I misread Steins wiring diagram, I put pin 6+9 to gnd and pin5+8 to the sending unit. I hope this didn't fry anything.
(Steins diagram)

From the G3X install manual rev K, page E-2 page 1 of 2 fuel quantity and fuel flow examples, I'm tempted to wire it like the middle example with just 1 wire pin 6+9.

But since I already have the 2nd wire ran I would rather hook it up to ensure a good ground and not have a loose wire. Using the top example it shows the gnd on pin 7 + 10 which differs from Steins diagram that uses pin 5+8 for gnd. Which pin should I use for the gnds?
Did I possibly hurt anything by hooking up these wires wrong?
Thanks,
Andy

 

[Bill.Peyton]

If you have the standard S/W resistive fuel float sensors, then you only have one contact and ground. You do not need the excitation voltage supplied by the GSU.
You are correct in your thinking in the middle example is how you would connect your sensor. Pin 6 and 9 to the center terminal of the SW fuel float. I would also run a return ground back to pin pins 7 and 10 respectively. I would remove the 5 & 8 pins from the connector You could use these to run your ground returns and reinsert them into pins 7 and 10. I do not think there is enough current to have damaged the resistive element in the floats nor the GSU. You can check these with an ohm meter. I would imagine the GSU has over-current protection.
Here is how I did it. Ignore the color codes on my wires. Also, do not use the rubber gasket that comes with the sending units as shown in my photo. These were changed out to cork gaskets with non-adhesive Permatex. Alternatively, use Vans method with pro-seal. Just make sure you have them bent correctly before you permanently seal them in!

 

[crabandy]

Thanks Bill, that's what I was thinking of doing.
I double checked the sending units resistance and bend when I reinstalled them with proseal only for the fuel pickup service bulletin.

 

[g3xpert]

Hello Andy,

Don't you have a GSU 73 instead of a GEA 24?

If so, the drawing on page E-7 shows the FUEL 1/2 wiring for a GSU 73 using resistive sensors.

These sensors are typically grounded to the airframe, but like Bill's picture shows, running a wire pair is a good way to assure a good ground.

Thanks,
Steve

 

[crabandy]

Steve,
I have the GSU25/GEA24, the pre-wired harness included a 2pair shielded wire for the fuel sending units. I think I might as well hook up a gnd, just to confirm I use pin 7 & 10 for the gnds on the sending units?
Thanks,
Andy

 

[g3xpert]

Steve,
I have the GSU25/GEA24, the pre-wired harness included a 2pair shielded wire for the fuel sending units. I think I might as well hook up a gnd, just to confirm I use pin 7 & 10 for the gnds on the sending units?
Thanks,
Andy

Hi Andy,

Yes, pins 7 and 10 on connector J244 are the Fuel 1 and Fuel 2 grounds for the GEA 24.

Thanks,
Steve