2000 M1123 Fuel Sending Unit Test Procedure

[dlr2112]

Good Day All-
I purchased a 2000 M1123 last September and it arrived this February. Since it's arrival I've been replacing a bunch of parts (all the rubber hoses, fuel pump(s), injectors, 1/0 electrical cable, etc). Before this work, my fuel gauge was operational. I removed the gage cluster when the truck was repainted, but when I reinstalled the gauge panel, I must've "Reversed" the wires in the fuel gage because it looks like it "Pegged" counter clockwise (or far below "E"). Are these gages polarity sensitive? Is there a chance I damaged the sending unit? I ordered a replacement gauge, but now I'm question the problem. It seems like I have 24v on the "Signal" wire, and that can't be good. I have the TMs, but struggling to find a test procedure to narrow down how the gauge failed. And it looks like the gauge needle actually bent when it went full CC.
I appreciate any insight.
Thank You-

 

[papakb]

Yes, they are polarity sensative. If you look at the connectors you will see one is smooth and one is ribbed. They need to be connected ribbed to ribbed and smooth to smooth.

 

[dlr2112]

Yes, they are polarity sensative. If you look at the connectors you will see one is smooth and one is ribbed. They need to be connected ribbed to ribbed and smooth to smooth.

Perfect. I didn't even notice that when I was making the connections, and still wouldn't've thought to observe that now (without your input). Thank you for the info! Just in time too, as the replacement gauge is arriving today.