Fuel Gauge Stuck At 3 O’clock ?

[54blackhornet]

Need help ! Just bought a new sending unit from Wes at Classic Heartbeat Pick Ups, super service I must say. Working on a three hole cluster, no gauges except speedometer and fuel gauge. Installed it, checked that I had good ground at sender. Still stuck at 3 o’clock ? I have read what Vette Vet said to check but not clear on open circuit on ground side ? Is there a fuse I’m missing ?

[RustyPile]

If all other items including the lights, are working on the instrument cluster, it's probably not a fuse issue.

One step for testing a faulty fuel gauge is to disconnect wire at sending unit and the gauge should go past the full mark. This tests the fuel gauge complete circuit, and indicates a working gauge.

In your case, if everything is connected, the "over full" gauge reading indicates an open circuit between the gauge and sending unit including the ground path of the sending unit. Things to check are, sending unit wire not making contact at the sending unit. Broken wire or bad connection between the sending unit and gauge. Be sure the instrument cluster plug is fully seated on the back of the instrument cluster. Using a suitable jumper, connect one end to the sending unit framework and the other end to a suitable spot on the body.

[zosoppp]

03:00 position of the fuel needle indicates that the sender circuit is open somewhere.

To start check the connection between:
a) tan wire and the fuel gauge socket in the fuse block
b) ground wire clip and bottom of dashboard opening
c) tan wire at the tank sensor pin

Also check the resistance between a known good ground in the cab and the metal at the tank sender metal, it's the ground path for the sensor voltage, and should be zero ohms or close to it.

[54blackhornet]

Thanks for the advice ! I pulled the entire wire from the fuse panel to sender and checked it closely. Checked it for continuity, good. Ran a separate ground to the sender body. This is an idiot light cluster, all the warning lights do work properly but the illumination lights do not ?

[dmjlambert]

Illumination is on a separate fuse. Do the brake and temp lights come on during engine cranking? Those are on the same fuse as the fuel gauge.

[bcfishon]

I vote bad sending unit.

[Sheepdip]

Did you verify the ohms reading on the new sender before you installed it? Could be a faulty sending unit.

[pjmoreland]

If you unplug the sender wire from the sender and then connect the wire to ground, the gauge should move to EMPTY (ignition in run position). If it does, then the issue is likely with your sender.

Is your sender wire plugged into the "Fuel Ga" terminal on the fuse panel?

[54blackhornet]

Thanks again ! Brand new sender from Wes , I have grounded the tan wire going to sender and needle won’t budge. I did check the sender and it said 0 to 90 stamped on it. If I pull it out to test it what’s the proper procedure for testing function ? I don’t understand why the needle won’t move when sender wire is grounded ?

[dmjlambert]

Do the brake and temp lights come on during engine cranking? Those are on the same fuse as the fuel gauge. If those warning lights don't come on during engine cranking, fix that problem first.

[RustyPile]

Originally Posted by 54blackhornet

Thanks again ! Brand new sender from Wes , I have grounded the tan wire going to sender and needle won’t budge. I did check the sender and it said 0 to 90 stamped on it. If I pull it out to test it what’s the proper procedure for testing function ? I don’t understand why the needle won’t move when sender wire is grounded ?

Assuming you did this test with key on, refer to the last paragraph in my first post.. Others have said the same thing.. There is a loss of continuity somewhere along the length of the tan wire, OR --- You have a bad gauge...

[54blackhornet]

Again I appreciate the help ! Yes the brake and temperature lights flicker during cranking. I ran a separate wire from sender body to the negative battery post with no results. I will pull cluster and check for any loose connections at plug…

[dmjlambert]

On my instrument cluster I used a small 12V battery to test it while it was out of the truck. I had to clean up the metal traces at the connector and I used some Brasso metal polish with a Q-tip to do that, made them nice and bright. One of the traces had lifted from the plastic and I was able to carefully glue it back down to the printed circuit plastic. I also cleaned the connector terminals on the wiring harness with some Brasso and a Q-tip and rag.

Slide a piece of business card or plastic under the printed circuit where the connector plugs in, to make sure the alligator clips don't touch the metal of the instrument cluster. Then you can use small alligator clip test wires to hook it up if you are gentle and careful. Clip the leads on for + power to the trace that would normally get power from the pink wire, and - power to the trace that would normally get ground on the black wire, or just connect - power to the case. Connect another lead to the - terminal of the battery and touch the free end to the connector traces at the various spots to observe the warning lights or movement of the fuel gauge to empty. You can see the route of the traces on the printed circuit to figure out how stuff connects.

Here is a detailed thread about fuel gauge testing. https://67-72chevytrucks.com/vboard/...d.php?t=640615

[Wrenchbender Ret]

On some models the wires going to the rear of cab go through a channel under the threshold at the edge of the carpet. This is a poor environment as they get corroded often & cause shorts & open circuits. If you get in back of the inst. panel & remove brown wire from the gauge & ground the term on the gauge the gauge should go to empty. If so you have an open in the wire from the gauge to the sender.

George

[54blackhornet]

I really appreciate everyone’s help it’s been close to 100 today so I didn’t go outside to pull the cluster. I did remove the tan wire completely and checked it closely, no bare wires showing and it checked fine with multi meter. Beginning to believe the issue is between the fuse panel and gauge. Tank is properly grounded, New sender so not much else to examine until I get the cluster out…

[LockDoc]

Originally Posted by 54blackhornet

I really appreciate everyone’s help it’s been close to 100 today so I didn’t go outside to pull the cluster. I did remove the tan wire completely and checked it closely, no bare wires showing and it checked fine with multi meter. Beginning to believe the issue is between the fuse panel and gauge. Tank is properly grounded, New sender so not much else to examine until I get the cluster out…

Try removing the fuse and cleaning the contacts on the fuse holder if you haven't already done that.

LockDoc

[Ryanz]

Originally Posted by 54blackhornet

I really appreciate everyone’s help it’s been close to 100 today so I didn’t go outside to pull the cluster. I did remove the tan wire completely and checked it closely, no bare wires showing and it checked fine with multi meter. Beginning to believe the issue is between the fuse panel and gauge. Tank is properly grounded, New sender so not much else to examine until I get the cluster out…

Did you ever get this resolved? I'm having the same issue.

[54blackhornet]

No I have not ! It’s been close to 100 by me so no truck tinkering until it cools down..Jack