How to test fuel gauge in dash 89 chev 2500 so I can tell if the gauge or tank unit is bad. The dash fuel gauge will change 1/4-1/2 tank overnight even if the truck has not been run.

The gauge could be bad or the sending unit in the fuel tank ! How to test fuel gauge tank sending unit P0463 GM

It could be the gauge on the dash or the sending unit in the fuel tank is bad. If it is the sending unit ,the gas tank will most likely have to be taken out. And if the dash gauge the dash will have to be taken apart. Diagnosis of Stuck Fuel Gauge Is it Gauge or Sending Unit Here is a video how to test it.

Most of the time it is the sending unit in the fuel tank.Remove the connection from the fuel tank,and using a test light,test the wires that you removed from the fuel tank. Clip the alligator clip on the test light to a good known ground,and use the probe on the test light to touch the terminals in the connector you unplugged.Make sure the ignition key is turned to the on position,right before start position.Have someone to watch the gauge.At this point the gauge should be showing past the full position.When touching the right terminal in the connector you removed from the tank,the fuel gauge should move down toward the empty mark.If this fuel gauge doe do this when you are testing it,then the gauge in the dash is good and the sending unit is bad.

It could be the gauge bad but most likely the sending unit which is located inside the tank is the problem--Usually does not happen on vehicles this new but you know how it goes. Fuel tank if sending unit there has to be removed.

Most mechanics will be able to test the fuel level indicator on the dash and my money would be the sending unit in the tank is bad.

You definitely have two different issues as the fuel gauge and radio are on different circuits. The radio could be a blown fuse, which would require finding a short circuit. The fuel gauge could be as simple as a bad connection at the sending unit or a lost ground on the fuel tank. Disconnect the fuel gauge at the tank and with a twelve volt test light well grounded probe the harness terminals with the key on (engine off). The fuel gauge should move when the sending unit wire is probed, and the test light should light dimly. Other terminals are a ground for the sending unit, a ground for the fuel pump, and power for the fuel pump. If the gauge moves when the sending unit wire is probed the problem is either the sending unit or a bad harness connection. If the gauge doesn't move during the probe there is a wiring problem (open circuit) or a bad dash gauge. Hope this helps.

Most likely it would be the tank sender unit,but it could also be the dash gauge and or possible wiring. When u turn off the key , does the gauge go to a different position ? If so, then probably the tank sender, if not then the dash gage.

the fuel level sendind units go bad on 90s dodges all the time. in the 10 years i worked for chysler i must have changed hundreds. ussually they will lie to you and tell you there is 1/4 tank when its actually emptie

fuel sending unit in tank but could be fuse or breaker. Are any other gauges not working? if all other gauges working probably not instrument panel fuse or cluster fuse. And if your not having problem with fuel getting to engine then more than likely your sending unit is not in with fuel pump.

Hi, sounds like you have checked everything properly and you have a bad tank sender, current when checked with test lamp should pulsate.I suggest replace fuel tank sender.

What was the original problem? Most fuel gauge problems are either a bad fuel tank sending unit or a bad ground wire going between the sending unit and the frame of the car. The gauge and wiring can be easily tested using only a 12 volt test lamp, once you have access to the wiring at the fuel sending unit. This often requires draining the fuel tank and lowering it from the vehicle.
To test the gauge in the dash and it's related wiring, connect the 12 volt test light between the wire between the gauge and the sending unit (the one with power in it with the ignition on). Make the connection near the fuel tank sending unit. Connect the alligator clip on the test lamp to a known GOOD ground. The bulb in the lamp should glow dimly. The dash gauge should read somewhere between 1/4 to 3/4 of a tank of gas. (Varies with make and model) This will verify that the gauge is either good or bad.