Odd left tank fuel sender issue

[FloridaMan]

Recently upgraded to an EDM-900 and having some issues with the left fuel sender. When the unit out of the tank, the range reads fine and as expected. With it installed, the range is very limited and reads as INOP on the ground, but comes alive up in the flight levels. Prior to the EDM-900, the cluster gauges were rock solid and dead nuts accurate from full to empty (though not repainted for the long range tanks). It would be nice if they worked for added situational awareness, but I have the least trust in electronic fuel gauges. My checking fuel consists of looking in the tanks before every flight and watching the fuel totalizer and the wing gauges in flight to make sure they agree with each other. 

[DonMuncy]

I am not sure your plane is the same as the later ones, but if you have two senders per tank, you have to watch the wiring carefully. The wire to the gauge runs through the unit. That is, it goes into the feed wire and does not go to ground. The screws holding the inner unit on the tank are insulated from the tank. That unit's body is then wired to the input wire on the outer sender, which then goes to ground.  Said another way, the inner unit is in series with the outer unit. Make sense?

[FloridaMan]

Yes. I'm aware they're in series. The IA who did the install thought the sender was stuck "up" which is why he removed it to inspect it. With it removed from the tank and in series, it seemed to work correctly. I don't know if resistance goes up or down with the fuel level. If it goes down when the fuel level is up then it would make sense to search for a short to ground. 

[ArtVandelay]

You can’t check the senders statically, you have to carefully check them as you move the arm, be sure they are changing regularly, no jumps in the readings.


Tom

[bill98]

19 hours ago, Antares said:

Recently upgraded to an EDM-900 and having some issues with the left fuel sender. When the unit out of the tank, the range reads fine and as expected. With it installed, the range is very limited and reads as INOP on the ground, but comes alive up in the flight levels. Prior to the EDM-900, the cluster gauges were rock solid and dead nuts accurate from full to empty (though not repainted for the long range tanks). It would be nice if they worked for added situational awareness, but I have the least trust in electronic fuel gauges. My checking fuel consists of looking in the tanks before every flight and watching the fuel totalizer and the wing gauges in flight to make sure they agree with each other. 

I'll do an even trade - my 830 for your 900. Now you won't have any issues with fuel senders!

[Shadrach]

You have two planes which one are you talking about?

[FloridaMan]

Sorry, it's the Rocket. 1981 M20K