Instrument cluster fuel gauge

Hello, strange things do happen like this, but before we condemn the instrument cluster, how much of the wiring harness were you having to move around under the dash while replacing the actuator?
And what sub-model is this 1500, 2500, 2500 HD, 3500 etc.? I've got the 1500HD pulled up in Mitchell to look at the wiring diagrams. Since it's one of the sub-models that had 2wd.
And does this model have dual fuel tanks? I just want to make sure I've got the correct information here.
or you can give me the Vin# and I can look it by that.
You can start your checks by inspecting the connector on the back of the instrument cluster. If the harness got pulled on a bit if could be just a loose pin on the connector, I'd say the chances are the harness got pulled somewhat since you were working in that area. I don't think you damaged the cluster, so that pretty much just leaves a harness issue. I will pull up some instructions on getting to the back of the cluster to check the connector. It may have more than one back there and since these harnesses run all over the place, it's easy for something to have gotten moved and not really noticed. it's odd that it flipped upside down like that. But get me some more info on the truck so I can get the correct diagrams for you.
Was it reading just the opposite of what it is now, so around half a tank?

Ok so there are about 4 Technical Service Bulletins on issues with the Fuel gauge reading incorrectly. I posted the most relevant below. Just 2 of them, But it seems the Fuel sending unit is to blame for this TSB. Theyre calling it the Fuel level sensor, There might even be a code stored in the Engine computer or possibly the body control module. Since the cluster receives the Fuel tanks level through serial data and the rest of the gauges are working. It may be a fault with the Fuel level sensor. Ill post an example of one of the Codes it might set if the Fuel level sensor is faulty because it uses the sensor for misfire and Evap Data. So you may want to take the truck to your local parts store and they will scan the truck for free for diagnostic trouble codes. If there are none. Then you may go after checking the connections on the back of the cluster.
Why there failures happen like this, I dont know, We've had vehicles come in for an oil change and the ignition coil happens to quick right there at the shop. It could have something to do with unplugging connectors to get into different areas under the dash, and that disturbed something, but with a few TSBs like this, maybe the dealership has to replace the fuel level sensor for no charge, You would have to call and see.

https://www.2carpros.com/articles/how-to-check-wiring

Well thank you for the compliment, I appreciate it. But keep an eye on that fuel gauge, let's see if the problem shows itself again when the fuel level gets down to where it was when it failed previously. Maybe the sensor is shorting out at that level. And since it's a data signal that's read instead of just a voltage signal, it's possible a module doesn't know what to do with a skewed signal and the gauge flops upside down. Or it could be a hot or cold related issue, but for now we'll just see how it goes. It is possible it's a cluster failure too, but we won't know until it happens again or fails altogether. If you need any other wiring diagrams or information just let us know. Sorry to hear about the funeral, hope your family is doing okay.

One other thing, certain devices that you can plug into a power port on the truck can cause interference with certain systems, just something to keep in mind. Or any aftermarket devices plugged into the Data Link Connector under the dash where a scan tool would be plugged into. Those can cause a lot of problems.