Onto a new issue....my gas gauge reads about 1/4 when the tank is full. Its an original sending unit that tested ok (10-76 ohm span). I get 8.5 ohms across it with the tank full for some reason. If I ground the sending wire it doesn't get much above 1/4. If I jumper the sending wire to the sending unit post its the same. My cluster has a new 5V IVR and new circuit boards. I did test it when it was out...I seem to remember that it would only go to 3/4 with 76 ohms. Any suggestions on what I can check?
Gas gauge reads low
- Thread starter 1MeanA
- Start date
-
10 ohms full, 76 empty ... give or take.
Sounds like you have a corroded connection in your sender to gauge wire that is creating resistance and the 1/4 tank reading.
Sounds like you have a corroded connection in your sender to gauge wire that is creating resistance and the 1/4 tank reading.
That would be good as it should be an easier fix. The rear harness is new so it would have to be between the kick panel and gauge board I guess.
WAG, but ground strap?
I got a permanent and temp ground wire on it.
Post a photo of the fuel gauge with the key off
Did you test the float? They sometimes fill with gas (or partially) and sink. I have also seen the float rod bend and catch on the pickup tube and not show "full".
Shorting his sender wire directly to gnd only has his gauge going 1/4 tank. He has a wire issue or gauge issue.
Unplug it from the sending unit. Use the DVM to measure resistance from the wire that was disconnected to the ground wire you have at the tank. Should be very close to 21 ohms (the value of the resistance wire in the gauge).
I get 0.425 kohms between the sending unit terminal and sending unit ground. Does this explain the issue?
I know there is because I put 3 Gerry cans in it and then went to the station and filled it until it sloshed out the filler
LOL, no it doesn't. "New" does not mean functional.
You are saying? grounding the wire does not peg the needle? Then wander up to the left side kick panel and spearate the harness. Pick the correct wire and ground it there. if it doesn't peg the needle, then the trouble is in the cluster.
If the temp gauge works OK, then try loosening/ tightening the gauge stud nuts. Check the condition of the harness connector pin at the circuit board. Check the terminal in the harness that mates with it.
You probably need to rig up the cluster out of the car and test it. You need to get/ rig test resistances, if you have a fuel sender, you can set it to different restances and use it.
Test resistances:
Bench Testing a gauge cluster
You said 74 ohms got 3/4 tank? Waaay off. 74 is supposed to be close to the empty hash mark. 8.5 is a bit low and would degrade the gauge over time. Even more so when the limiter was also producing heat in that can. I can agree to possible saturated float.
I have to ask what method was used to elimate the original limiter from the circuit?
I have to ask what method was used to elimate the original limiter from the circuit?
That is a problem for sure. Good ground wire between the instrument cluster and the dash and the dash to the body?
Low resistance would make the gauge read closer to full
When the float is lower in the tank that is higher numerical resistance and the gauge reads closer to empty. When higher in the tank the resistance is numerically lower and the guage reads closer to full.
The photo shows the fuel gauge needle on the left side of the E, typically that indicates the gauge has been damaged. My temp gauge took a hit and the needle sat about the same place. It still worked but the normal, normal operating temp location was just past the cold line.
If I recall correctly there is a dash frame to body ground (passenger kick panel). I have grounds from the IVR to circuit board screw and cluster frame. I don’t recall having a dash to cluster ground wire. The other gauges work but all seem slow to respond.
That is what I was saying I think. The tank is full and the sender resistance is only 8.5 ohms which should be fine. I think I tested it at 11 ohms on the bench (full). I do fear the gauge is no good.
If the resistance is 8-11 the guage should read full, if it does not, either there is a bunch of resistance in the wires and connections or the gauge is toast
Some rally inst panels did have a short ground wire at the noise cap. Ground behind left kick panel comes from heater case. I was told it's related to static charge in the heater case and core. When I ad a ground wire from inst' panel I do mirror the right side behind left kick. My wire disconnects behind the column door. I can remove bolts and lower the column without loosing my ground. I asked about how the original limiter was address but no answer yet. Internet shows how to create a problem there.
I think I have the wire where the cap was. It has an IVR as mentioned so the mechanical limiter has been defeated.
My query was in what manner it was defeated. To bend the limiter beam with needle nose plier can create a problem. The winding insulation. Is barely that. Fine fiber, spiral wound. Break the insulation in bending. Short the wire to the beam. Failed to isolate the gauge can from chassis ground. Result is equilivent of a 4th and faulted gauge in the circuit.
I think the beam was bent. I'm not sure I follow the rest of your comment. I can add some ground even if temporary to see if anything changes. It will be a winter fix which isn't that far off up here.
The typical thermal gauge is isolated from chassis ground. Only current path possible is low voltage out to sender. This 3 post gauge IS NOT TYPICAL. Lift it to reveal an unpated spot in housing where a slither of metal ground the limiter. Yes the gauge has 3 contacts showing like the plug in type limiter. Absolutely had to be a 4th contact somewhere. You regulators output can and will.backfeed through remnants of a limiter bent or not. All anyone ever needed to do was place a piece of tape under the can. Or complete the paint job. LMAO
-
Similar threads
