66 Dart gas Gauge

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rod7515

rod7515

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I have a non functioning fuel gauge on my Dart. What are the trouble shooting steps I need to go thru? I see only one wire to the tank unit. I have not checked anything yet. What is the wiring on the back of the gauge? Is there a second wire coming off the gauge anywhere?
Thanks Rod
 
I think that there's a voltage limiter in there, it runs the temp gauge as well..... Is the temp gauge working??
 
Pull the wire off the fuel tank and ground it (the wire) for several seconds with the ignition on. Have someone watch the gas gauge. Don’t leave it grounded for a long time (more than about 30 seconds max) or you risk damaging the gauge. If the gas gauge moves, it is likely the sender. If nothing happens the problem may be elsewhere.
 
First requirement is a working limiter... Even though not using the temp gauge you should still have that purple sender wire. If the limiter is working your meter will show a pulse voltage on this wire with switch on, 2.xV, 3.xV .
You can find the fuel sender wire (dark blue) in a harness connector behind the left kick panel. Same pulse voltage should be found there. Short it to ground. If gauge is good the needle will move to max full.
If the limiter isn't working we'll figer out why not.
 
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If you have an original instrument cluster (I am referring to a early 70s model, not sure what year you have) the two screws coming out the back of the gauge get connected to the PCB when you tighten down the nuts. One is connected to the +12vdc and the other goes to the sending unit. There really should be no wires involved, just the traces on the PCB. The circuit is grounded at the sending unit. There is no need for a ground at the gauge.

Do you have a working set of schematics? If you do electrical work, you really need a set
 
Pawned said:
If you have an original instrument cluster (I am referring to a early 70s model, not sure what year you have) the two screws coming out the back of the gauge get connected to the PCB when you tighten down the nuts. One is connected to the +12vdc and the other goes to the sending unit. There really should be no wires involved, just the traces on the PCB. The circuit is grounded at the sending unit. There is no need for a ground at the gauge.
Click to expand...
The typical 2 post thermal gauge is connected to a voltage limiter, not 12 volts.
I don't recall where a 66 Dart has its inst' voltage limiter. If the fuel gauge is a three post gauge the voltage limiter is inside. The three post gauge 4 connections, 12 volts in, limited voltage out, sender, and has a slither of metal on its backside that sits against a small unpainted spot in back of the inst' housing. This is where the limiter gets its ground. In some cases loss of this ground was why the limiter and gauges stopped. Clean it up, snug it up and all work again.
 
RedFish said:
The typical 2 post thermal gauge is connected to a voltage limiter, not 12 volts.
I don't recall where a 66 Dart has its inst' voltage limiter. If the fuel gauge is a three post gauge the voltage limiter is inside. The three post gauge 4 connections, 12 volts in, limited voltage out, sender, and has a slither of metal on its backside that sits against a small unpainted spot in back of the inst' housing. This is where the limiter gets its ground. In some cases loss of this ground was why the limiter and gauges stopped. Clean it up, snug it up and all work again.
Click to expand...
I stand corrected, I should have said supply voltage not 12vdc. As I stated, I did not know what year the vehicle is, as I stated "(I am referring to a early 70s model, not sure what year you have)"
 
I know i havent been back to update this thread but its time to start and resolve this issue. I plan on digging farther into this gauge sometime this weekend. Any help that you can send my way would be greatly appreciated.
redfish,
You speak of a limiter. Can you show any pics of this. The wiring digram I am looking at does not show that at all. Also where would i find this limiter? On backside of dash or somewhere else?
Here's what I did tonight. First let me say the gauge is on the empty at all times.
First I ran a ground wire from the tank to the frame and checked gauge but had no movement. Then I remove the fuel sender wire at the tank unit and grounded it and again no movement at the gauge. Then I disconnected the wire connector(drk blue wire) at the kick panel and tested the continuity from the sending unit wire to the kick panel connector. That tests good. I couldnt get up under the dash because the car is on the lift and the door wont open all the way so I will wait until the weekend to test any farther.
Would anyone have a pic of the back side of a 66 dash? Im going to try to work on this without removing the dash from the car because of the tach being mounted to the steering column.
Is there a more detailed wiring diagram that I should be looking at? I will post the pic of the wiring diagram that i have just below here.
66Dart wiring diagram A.jpg
66Dartwiring diagramB.jpg

If there is something better thenthese diagrams let me know where i can get them.
Thanks, Rod
 
It's a metal can about a inch long and a half inch wide. It plugs into the printed circuit on the 66 Dart dashes and has 3 prongs If my memory serves me correctly. One thing nice about grounding the wire at the sender, if the gauge moves to full, it tests all the wiring and the gauge. That eliminates a lot of wiring.
 
I assume that toolmanmike is correct, that on a 66 dart the "limiter" is replaceable. My 66 Barracuda has it built in to the fuel gauge.
Does your "temp" gauge work?
Hopefully someone more knowledgeable can correct me if I'm wrong here......but I believe the "temp" & "fuel" both get the 5.5v off the limiter, therefore if the temp works..you probably could go directly to the gauge itself.

If both do not work, certainly the limiter is suspect. I believe I have one or two

voltage limiter.jpg


This is what I think you're looking for
 
As I said I one of the first replies I am not using the temp gauge since I have aftermarket gauges. The only thing that I will be using in the original dash is the fiel gauge and speedometer.
Thanks Rod
 
You could take four "D" batteries in series to duplicate the current. 6V won't hurt the gauge.

Please read it all, because I don't exactly know what your gauge cluster looks like.

3 POSTS SCENARIO
  • Pull out the gauge cluster
  • follow the printed circuit pattern, on the circuit board, to the mounting screw to determine the "ground", trace it back to one of the three fuel gauge posts and attach the neg lead to that post
  • of the three posts coming out of the fuel gauge, the other two posts are "voltage limiter in" and the other is fuel gauge. You can put the positive lead to either. If the gauge does nothing ( give it a second or two ), move the positive to the other screw. If your gauge is good, then the gauge will move to "full".

CAN TYPE VOLTAGE LIMITER

  • Pull out the gauge cluster
  • follow the printed circuit pattern, on the circuit board, to the mounting screw to determine the "ground", trace it back to one of the three "voltage limiter" prong sockets (voltage limiter pulls straight out) and attach the neg lead to that prong socket ( you can use the metal of the gauge cluster, but the socket is better)
  • of the three prong sockets of the voltage limiter, the other two sockets are "voltage limiter in" and the other is fuel gauge. You can put the positive lead to either. If the gauge does nothing ( give it a second or two ), move the positive to the other screw. If your gauge is good, then the gauge will move to "full"


  • You won't hurt the limiter or gauge if you choose the wrong post, as the only effect would be to cut your battery voltage approximately in half. A paper towel tube or flashlight body can be used to hold the batteries
That's my thoughts. I hope this helps you.....it's what I would do.

Does someone else want to tell me this will NOT work? Let's help the man out.
 
It would really help if the OP would simply ground the wire at the tank to diagnose his issue. This procedure has been used for a half a century to diagnose fuel gauge issues. The gauge won't operate properly if the tank/sender is not grounded properly. There is a ground strap that connects between the fuel pipe on the sender and the fuel line.
 
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Tolman mike, in post #9 you will see I have already done that with nothing happening. I know I have a solid wire from tank unit to kick panel connection so I'm going to have to go inside up under dash. That's a weekend job after I get the car off the lift. I'm looking for where to go and how to trouble shoot from here. The tank and sending unit are new back when I bought it 6+ years ago and to be honest since I never drove the car I cant tell you if it worked ever since i had it. Its probably going to be back side of dash wiring or limiter but I just need to find easiest way to troubleshoot it.i haven't looked there at all. Hell I might not even have wires hooked up oan gauge! I'll find that out this weekend.
Rod
 
rod7515 said:
Tolman mike, in post #9 you will see I have already done that with nothing happening. I know I have a solid wire from tank unit to kick panel connection so I'm going to have to go inside up under dash. That's a weekend job after I get the car off the lift. I'm looking for where to go and how to trouble shoot from here. The tank and sending unit are new back when I bought it 6+ years ago and to be honest since I never drove the car I cant tell you if it worked ever since i had it. Its probably going to be back side of dash wiring or limiter but I just need to find easiest way to troubleshoot it.i haven't looked there at all. Hell I might not even have wires hooked up oan gauge! I'll find that out this weekend.
Rod
Click to expand...
You can test the limiter by removing it, hook up 12v in and ground and measure the output. There should be a fluctuating reading between 0 and 7 volts.
 
rod7515 said:
Tolman mike, in post #9 you will see I have already done that with nothing happening. I know I have a solid wire from tank unit to kick panel connection so I'm going to have to go inside up under dash. That's a weekend job after I get the car off the lift. I'm looking for where to go and how to trouble shoot from here. The tank and sending unit are new back when I bought it 6+ years ago and to be honest since I never drove the car I cant tell you if it worked ever since i had it. Its probably going to be back side of dash wiring or limiter but I just need to find easiest way to troubleshoot it.i haven't looked there at all. Hell I might not even have wires hooked up oan gauge! I'll find that out this weekend.
Rod
Click to expand...
Sorry, I read the first part of post #9 but not the whole thing.
 
Just wanted to update this post. First let me say thanks to all of you that threw information out to me on this task.
As I said in an earlier post I had already grounded the tank to the body, also grounded the sending unit wire with no success. I had also verified that the wire from the tank to the kick panel connector was good.
So today I finally got around to more testing. First, I didnt want to remove the dash because I have my tach mounting into the steering column so I would have to remove that as well as I knew that one of the dash screws (upper right hand corner) was behind the center heating panel so that would need to be removed as well. As it turns out I couldnt see **** from the under side so I had to remove that stuff. Damn that makes the job so much harder. SO off comes that stuff and I remove the dash. Now the dash is laying on the floor and its time to test things.
So I remove the limiter and using a battery tender I apply power to the middle terminal, a ground to the long terminal then take my volt meter and find I have fluctuating current on the end terminal. That was a good thing! (What I still dont know is why the condenser connected to this circuit?)
20190818_172449.jpg

As I study this board I decide to clean the terminals on the limiter. Then again using the battery tender I apply power to the 2nd terminal on the pic below as well as ground to the 1st terminal. I then checked the 3rd terminal of the limiter for power and found a pulsating voltage. Again a good thing!
20190818_172503.jpg

Below is a pic of the underside of the limiter. You can see I did a quick clean of the terminals. I did go back and do a better job! You can also see that condensor that I spoke of earlier goes into the middle power feed terminal. (I cleaned it as well)
20190818_172524.jpg

All put back together below and the 2 nuts are the gas gauge terminals. I tested the one on the right and found I had fluctuating power so I went and grounded the first nut/prong. Checked the gauge and it went to full. When I take the ground away it goes to empty. So I know the gauge works!!
20190818_172551.jpg

Of course I ran out of time at that point so tomorrow I will check the wiring from the kick panel connector to the gauge. I believe that I probably had a bad connection at the limiter but I need to test the rest of the circuit before putting it all back together.
Again, I couldnt trouble shoot this circuitry without all the help from you guys here. Thank You All!!
Looks like I should be able to get a working fuel gauge sometime this week!
Again thanks,
Rod
 
These gauge units are known to have weak ground connection, you might consider adding another while your there.

I believe the condenser is there because the limiter would be heard through the radio

Lets us know the final conclusion
 
Loose or broken pins at those inline harness connectors are too common, especially the ones near top of board. I wont say you should add solder at the pin to board connections but a little dielectric grease and be very careful with them is said.
I couldn't stop short of new limiter or solid state regulator, and all new light bulbs and sockets while I'm there. I've lived the "one problem after another" period and became quite proficient in inst' panel R&R. I learned, clean every electrical contact point, add dedicated chassis ground wire, bypass amp gauge, covert it to volts gauge where possible, everything i can do to prevent repeating inst' panel R&R.
Resealing wiper pivots is a totally different service and thread topic but is relevant. Working through the dash is much easier than working under it.
 
Try a new headlight switch, made a big difference in my 66...
 
Coalman, Not sure what you are referring to with a new headlight switch?? Can you explain? I replaced the switch during the build so it is new.
Well last night I checked the wiring from the kick panel to the dash connectors. I found everything to be ok, however I also found that the wires inside the connector could push backwards allowing them to slip out the back of the connector as you push the plug over the dash terminals.
I put dielectric grease on all the connections . Then I put the connector on making sure the wire terminals stayed in place. Put the cluster back into the dash and tightened everything up. Went back to the tank and connected the wire to the sending unit.
Now its time to see if the gauge is going to work. I pulled the cut off switch to supply power, sat in the car and turned the key on and wollla! the gauge moves to about 1/8 tank. Thats probably correct because the last time I drove it I ran out of gas and I put in a few gallons to get back home where I parked it and said the gauge needs fixing before I do anything else.
So I can now cross this off my to do list!
Now to move on to other issues which include, shielding fuel lines from heat, figuring out how Im going to run a speedo cable around the headers, installing seat belt harness, rewiring the one wire alternator.
Again thanks for all your help in getting this issue resolved. I appreciate all the help
Rod
 
Yours, must be good. What had happened on mine was my gas gauge would read sometimes and then it wouldn't. I noticed if I pulled the headlight switch in and out it would work, also tapping the dash above the switch sometimes that would work. The real kicker was when I replaced the switch the temp gauge started to work. I had replaced the temp sending unit a long time ago and it never worked. So that is the story..
 
Coalman, that's strange because they dont use the same grounds or power feeds. But on these old cars you just never know. I'm just glad mines working now!!
 
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