Fuel gauge Intermittently worked,..now nothing. 66 Valiant

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FURY440

FURY440

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My fuel gauge Intermittently worked in my 66 Valiant. Now it seemed to stop for good. All my other gauges work. I grounded the sender wire and the fuel gauge doesn't move. With that said, is the instrument cluster hard to take out? If so does anyone know how it's done? I see four screws that holds it to the dash, but after that,.not sure what else needs to be removed so I can test the sender wire for continuity or see if anything is disconnected or broke. Does the sender wire go directly to the gauge?
Thank you....
 
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FURY440 said:
My fuel gauge Intermittently worked in my 66 Valiant. Now it seemed to stop for good. All my other gauges work. I grounded the sender wire and the fuel gauge doesn't move. With that said, is the instrument cluster hard to take out? If so does anyone know how it's done? I see four screws that holds it to the dash, but after that,.not sure what else needs to be removed so I can test the sender wire for continuity or see if anything is disconnected or broke. Does the sender wire go directly to the gauge?
Thank you....
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How old is the sender? When I pulled mine from 66 dart, it was completely rusted and rotted through.
I ended up with a new sender unit and also an aftermarket gauge that I mount at the bottom of the dash.
 
Not sure about the sender, but I grounded the sender wire to check the gauge and it didn't move.
 
FURY440 said:
Not sure about the sender, but I grounded the sender wire to check the gauge and it didn't move.
Click to expand...
gauge could be totally shot.
You need to remove the dash, it is not fun. on my dart you need to remove the heater controls and radio plate in order to get to all the screws. not sure about your valiant
 
Thank you. That was a good read. I'll be doing some testing today. It's not the sender as I said. I grounded the sender wire and gauge stays at empty. Time to trace the sender wire forward to see if it's broken anywhere.

When the weather breaks,.I'd like to remove the sender and check it. Are these still available?
 
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If it seemed to go on and off, seemed to read correctly when it was on, there's a broken current path somewhere. These instruments have their steel mounting posts swedged into a weak fiber board. So a weak pal nut was used to secure the post to the printed circuit board. So yeah a pal nut is part of the current path. Over time, the materials distort, vibration effects, those nuts can get loose. If fuel gauge is the only part of the panel that doesn't work, I would first find that sender signal wire behind the left kick panel and test there.
If I must pull the panel, I'll clean and tighten all contacts, bench test everything, add a chassis ground wire, all new light bulbs, do it all and be done with it.
 
RedFish said:
If it seemed to go on and off, seemed to read correctly when it was on, there's a broken current path somewhere. These instruments have their steel mounting posts swedged into a weak fiber board. So a weak pal nut was used to secure the post to the printed circuit board. So yeah a pal nut is part of the current path. Over time, the materials distort, vibration effects, those nuts can get loose. If fuel gauge is the only part of the panel that doesn't work, I would first find that sender signal wire behind the left kick panel and test there.
If I must pull the panel, I'll clean and tighten all contacts, bench test everything, add a chassis ground wire, all new light bulbs, do it all and be done with it.
Click to expand...

Thanks. Yes the gauge did work and read correctly when it worked. I plan on checking the connector behind the kick panel. The interior is out anyway. Well everything but the seats. If I need to pull the cluster,.I will change the bulbs and tighten all the connectors. Hopefully this will be an easy fix.
 
Just incase ... Please know the amp gauge is red hot at all times. Remove the neg' battery cable before going at the panel removal.
Most will attach the wiring and attempt to test the panel before completing the reinstall. It wont work without its chassis ground path. That is though the screws that attach it to the dash ( like most everything else on these vehicles ). Adding a actual wire for ground is recommended. Good luck with it.
 
OK,.after testing the kick panel connector,.I have a pulse reading while the key is on and the connector is disconnected from the other end going back to the rear of the car, but what is strange is if I connect the connector together and test the sender wire KO there is no pulse. Is this normal? What that said, I would assume the limiter is working since I have a pulse reading. I have good ground to the dash cluster also and Temp gauge is working and volt gauge. What do you guys think? Bad fuel gauge?

Looks like a ***** to get the cluster out.
 
You do have a pulse signal going through the fuel gauge and on toward the sender. So the winding in that gauge isn't burned open. Ground the pulsing wire right there and check for needle movement.
Keep these tests brief. Zero resistance will cook a gauge.
When connected you should find the same pulse voltage under the car at the sender. And there have been cases where the wire was broken in the trunk area.
So now I'm wondering about your earlier tests under there? Like where did you ground that sender wire for test. There's a ground jumper over the rubber fuel hose at the sender that sometimes looses connection. Has had come and go connection with weather conditions. Anyway... If that jumper faults, grounding to the sender body wouldn't proof. Lets be absolutely sure which is the fault, sender, gauge, connections, before we pull the panel.
 
RedFish said:
You do have a pulse signal going through the fuel gauge and on toward the sender. So the winding in that gauge isn't burned open. Ground the pulsing wire right there and check for needle movement.
Keep these tests brief. Zero resistance will cook a gauge.
When connected you should find the same pulse voltage under the car at the sender. And there have been cases where the wire was broken in the trunk area.
So now I'm wondering about your earlier tests under there? Like where did you ground that sender wire for test. There's a ground jumper over the rubber fuel hose at the sender that sometimes looses connection. Has had come and go connection with weather conditions. Anyway... If that jumper faults, grounding to the sender body wouldn't proof. Lets be absolutely sure which is the fault, sender, gauge, connections, before we pull the panel.
Click to expand...

Here is a video of the tests I did inside the car. I really don't want to pull the cluster if at all possible. I believe I did all the right tests.
[video][/video]
 
OK so if you're absolutely sure the pulse voltage was grounded for test ( we didn't see how/where ), and the needle doesn't move at all, that needle is stuck in place at home or separated from the bi-metal that moves it.
I've found these bi-metal strips and winding so caked with crud that it cant move ( like a plaster cast on an arm ).
The panel isn't really so difficult to R&R. the procedure is detailed in factory service manuals.
If I tried to type it all here from memory I would likely skip some step(s).
 
RedFish said:
OK so if you're absolutely sure the pulse voltage was grounded for test ( we didn't see how/where ), and the needle doesn't move at all, that needle is stuck in place at home or separated from the bi-metal that moves it.
I've found these bi-metal strips and winding so caked with crud that it cant move ( like a plaster cast on an arm ).
The panel isn't really so difficult to R&R. the procedure is detailed in factory service manuals.
If I tried to type it all here from memory I would likely skip some step(s).
Click to expand...

I'm just hooking the red probe from the MM to the sender wire going to the gauge and black going to ground on the MM. I turn the key on and I get pulse. If I ground that sender wire going to the gauge with the MM still hooked up I get no pulse and the gauge doesn't move. So, yes I don't get pulse voltage when I ground the sender wire. I even went as far as to run a temporary new wire back to the fuel tank sender and I get the same results.
 
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65 Valiant instrument panel isnt that hard to pull, just 4 screws and remove the screw on speedo cable..IIRC. Its been a while.
 
I'm really not sure why the pulse voltage would go away. Can a faulty limiter operate 1 gauge, within reason at least, but not operate 2. Heck anything is possible, even if not typical.
The pulses are supposed to be 2.X and 3.X to average about 6 volts. Much easier to measure with analog meter.
Just for fun... I would disconnect the temp sender and retest the fuel gauge for the slightest movement.
If the fault does turn out to be the limiter, or just a failing connection there, it's best to pull the panel to replace it.
 
Ok got it sorted. The dash cluster was very easy to remove,, about 15 minutes to get out. I found that the 2 nuts that hold the fuel gauge were corroded slightly and a bit loose. So, I went ahead and removed them one at a time and used 400 wet/dry sandpaper and clean the circuit board and the nuts. Did this for every connection on the cluster and replaced all the bulbs. As soon as I cleaned those points the gauge fired right up. It was just bad connections and loose mounting nuts. All is good now and time to take it for a ride..!! Thank you everyone for all the help.
 
So post #7 held the answer. This is very often the condition found at 3 post fuel gauges too.
Their engineers put a slither of metal on the back of that gauge to create the internal limiters ground path. Then so much more heat present = more part distortion, thus limiter operation fades.
A volt meter will show a minuscule amount of voltage continuity yet the needed amperage isn't conducted. Explains the disappearing pulse reading too.
Ohms measuring always tells the rest of the story. Happy moparing
 
RedFish said:
So post #7 held the answer. This is very often the condition found at 3 post fuel gauges too.
Their engineers put a slither of metal on the back of that gauge to create the internal limiters ground path. Then so much more heat present = more part distortion, thus limiter operation fades.
A volt meter will show a minuscule amount of voltage continuity yet the needed amperage isn't conducted. Explains the disappearing pulse reading too.
Ohms measuring always tells the rest of the story. Happy moparing
Click to expand...

Yes that was it the entire time, but I'm glad I went through the tests. Pretty simple circuit. I learned something at it was fun figuring it out. I'm just happy it's fixed and only cost me my time. Thanks again for the help.
 
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