Gas gauge not working? I think I fixed it.

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Pawned

Pawned

N.R.A. Lifetime Member - And damn proud of it
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Since the day I picked up my 71 Duster, I have put in many many hours trying to fix the gas gauge. I finally discovered that the gauge did not need to be fixed.


I started with replacing the original fuel sending unit. Parts of it were missing and more than likely dissolved in the muck at the bottom of the fuel tank. Then I replaced the mechanical voltage regulator with a 5 vdc electronic voltage regulator. Thinking I am smarter than I am, I decided that I could tweak the gauge by adding resistance in series of the sending unit, Didn't work. Then figured I could reduce the resistance by adding resistance in parallel to the sending unit. Still did not work.


The PCB voltage regulator died a unspectacular death, so I pulled the instrument cluster again. This time I took a couple hours playing with the resistance on the test bench. You would think I would know better.


Thinking, the resistance in the sending unit is where it should be, the gauge was working but not as I liked it. So if the resistance of the circuit is set to OEM specs. What is the one thing that I had not tried to adjust. Back to Ohms Law, VOLTAGE


I set a resistor to match the sending unit and attached my variable power supply and adjusted the voltage to the circuit. Eureka …..... I went and bought a 5 and 6 vdc regulators, $1.59 each.
As the temperature gauge was working just fine at 5 vdc it needed to stay there. As in the picture I cut the trace on the PCB so the two meters can use separate voltages. In the picture the PCB has been modified a few times prior to this.
I attached the 6vdc regulator to the gas gauge and the 5 vdc regulator to the temperature gauge.
Prior to this time the gas gauge would read either full or empty, nothing in between. NOW the gas gauge is showing I have ¼ tank of gas left (Which is about correct)


I think I done it. I will keep an eye on it to see what happens when I add gas 2 gallons at a time. :salut:
 

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good info

if it works, you may have just solved a problem we all seem to have...and will need better pics to complete our repairs.
 
I hate to be the bearer of news, but what you have done here is re--invented the wheel. There's many before you on Al Gore's internet who've installed 5V regulators

But.......you did discover, figure out, and fix it yourself. You get a lotta points for that.
 
67Dart273 said:
I hate to be the bearer of news, but what you have done here is re--invented the wheel. There's many before you on Al Gore's internet who've installed 5V regulators

But.......you did discover, figure out, and fix it yourself. You get a lotta points for that.
Click to expand...

You missed the point, the temp gauge needs the 5vdc regulator, but I put a 6 (six) vdc regulator on the gas gauge. The regulators are side by side.

The fuel gauge needs the extra voltage to kick it in the butt. It is only one volt more but that one volt is 17% more than it was.
 
i would love better pics and exact info as to what i need to do, and do you walk into auto parts store and ask for 5 and 6 volt regulators!? i admit electronics is not my strong point. if fact i'm almost 66 and not sure what i will be when i grow up!?? thanks
 
I filled it with gas today. I thought I set the phone on video to record the gauge but I can not find it, if it did.
Somehow I got some still pix of the refueling. The one thing for sure is the tank reached full as the guage did. Now I need to get it to empty and see what the gauge does.

The pix of the back of the pcb. I tried to add colors to show the different wiring. the +12vdc and ground are connected to both regulators. They have separate outputs
 

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barbee6043 said:
i would love better pics and exact info as to what i need to do, and do you walk into auto parts store and ask for 5 and 6 volt regulators!? i admit electronics is not my strong point. if fact i'm almost 66 and not sure what i will be when i grow up!?? thanks
Click to expand...

These voltage regulators are not found at the auto parts store. The +5 vdc can be had at Radio shack for $2. I do not think they have the +6vdc regulator.
You need to call around to the various electronics parts stores to get the +6vdc.
The tech sheet on the NTE962 6vdc+ regulator is at http://tinyurl.com/kh64jjv. At the bottom of page two is the drawing of what you should be looking for. The +5vdc regulator is NTE960. But that is only one company that makes it.
On ebay, I typed in the NTE962 and this is the page that came up http://tinyurl.com/mh9so97. Looks like they want around $5 for the unit.
I paid $1.55 each for mine.

Hope this helps
 
Pawned said:
You missed the point, the temp gauge needs the 5vdc regulator, but I put a 6 (six) vdc regulator on the gas gauge. The regulators are side by side.

The fuel gauge needs the extra voltage to kick it in the butt. It is only one volt more but that one volt is 17% more than it was.
Click to expand...

You're right I did, but on the other hand since replacement "solid state" ones are available, is it possible this is your specific gauge sender?

That is, all these gauges should have the same scale, whether oil, temp, or fuel.
 
The sender has the proper resistance at full and empty 9.6 ohm & 76 ohms
 
thanks for the followup, it would be nice to have gas gausge and temp gauge that works! LOL, i read about all the placesguys hookup aftermarket temp sender, i tried adding extension at side of block but appearantly does not work there, next i might try at thermostat housing. riding down the road with extra gas in can makes me feel like a mobile moliviv (spelling?) coctail! LOL
 
barbee6043 said:
i would love better pics and exact info as to what i need to do, and do you walk into auto parts store and ask for 5 and 6 volt regulators!? i admit electronics is not my strong point. if fact i'm almost 66 and not sure what i will be when i grow up!?? thanks
Click to expand...

One other suggestion, I only say this because you say that electronics is not your strong point. When you solder the wires to the pins on the regulators, use a heat sink and do not over cook the solder.

"Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body. You can buy a special tool, but a standard crocodile clip works just as well and is cheaper.

Also I bend the pins to have more room to solder. The two outside pins I bent to a 45 degree angle away from the other pins. I also use shrink tubing for extra insulation.
 
67Dart273 said:
That is, all these gauges should have the same scale, whether oil, temp, or fuel.
Click to expand...

I agree with you Mr. 67Dart273, the problem he experienced must be with his specific fuel gauge. This fix should not be appropriate for everyone.

Also, they make variable VRs that can be tweaked to get any range of voltage readings out of them for extra fine tuning, should this help anyone. For example, you may want 5.7 volts to get to the full reading, so after filling the tank, just adjust the variable VR until it reads "full".

I like the way you worked to figure out a solution for your problem. However I would have suggested replacing the gauge with one that had fewer hours it before going thru all the trouble you did. Though maybe your pride (deserved) and satisfaction was worth your efforts. Kudos to you sir!
 
68gtxman said:
I agree with you Mr. 67Dart273, the problem he experienced must be with his specific fuel gauge. This fix should not be appropriate for everyone.

I like the way you worked to figure out a solution for your problem. However I would have suggested replacing the gauge with one that had fewer hours it before going thru all the trouble you did. Though maybe your pride (deserved) and satisfaction was worth your efforts. Kudos to you sir!
Click to expand...

As it happens, I have two fuel gauges here at the house. I did the same setup on the spare gauge I have and got the same results.
But you are correct in the statement that no two gauges are alike. No two brand new gauges are alike either. 6 vdc is not the ideal voltage for everyone, but it gets old gauges to work and then people can adapt the gauge settings for themselves.

A 5vdc gauge is like a broken watch, It gives the correct reading twice a day. A 6vdc gauge may not give a perfect reading, but it is a lot better than a broken gauge.

No two cars are alike but people are constantly giving advise to fix problems. I have benefited from that advise and am appreciative. Why is it when I got advice on the KD linkage on my car, that no one jumped in to warn me that not all KD linkages are alike? Maybe I should buy a new linkage to make sure it works properly?

I guess I am a little sensitive as I probably have more than 30 hours trying to find an answer to this. I have surfed the web looking for an answer to this and nowhere could I find a fix that came close to working.
I found a fix that fixes my gauge and will probably get most other gauges working with a reading in the ballpark.
I am feeling attacked. Maybe next time I should keep my fixes to myself
:violent2:
 
Pawned, I appreciate you sharing this with a lot of us that haven't figured it out on our own. Ever since I swapped to new 5 vdc regulator from a member here and new sending unit I have been getting inaccurate reading ever though my ohms checks out in range. Hopefully this is the solution we have been searching for. Thanks for sharing, Joe
 
No one ever wants to listen to me. IF you have an aftermarket Sender...they are non linear and the original gas gauges were meant to read linear fuel senders. There is about 4 threads on this and if you look it up on google, many others not just mopar guys are having this issue with after market gauges....for the reason that the autometer mustang/chrysler gauge has the same issue.
 
red67gts said:
Pawned, I appreciate you sharing this with a lot of us that haven't figured it out on our own. Ever since I swapped to new 5 vdc regulator from a member here and new sending unit I have been getting inaccurate reading ever though my ohms checks out in range. Hopefully this is the solution we have been searching for. Thanks for sharing, Joe
Click to expand...
Joe, it was my pleasure
 
Pawned don't feel attacked and thanks for posting your findings and your work process to your results.
I have been lurking waiting to see how this would work out for you and found it very interesting and informative.
I am not presently working on my guages but it is likely I will be soon. I am always glad to see post from folks like yourself who have been their before me to make it easier for us guys that doesn't know where to turn with a repair.
Nice to see your efforts rewarded with a working gauge.
Hope I don't need this repair on my cars, but thanks for sharing even if I don't.
Remember people are on the side lines tuned in even if they don't join with a comment.
I am impressed and at the very least came away with some good soldering tips for resistors.
 
ssba said:
pawned don't feel attacked and thanks for posting your findings and your work process to your results.
I have been lurking waiting to see how this would work out for you and found it very interesting and informative.
I am not presently working on my guages but it is likely i will be soon. I am always glad to see post from folks like yourself who have been their before me to make it easier for us guys that doesn't know where to turn with a repair.
Nice to see your efforts rewarded with a working gauge.
Hope i don't need this repair on my cars, but thanks for sharing even if i don't.
Remember people are on the side lines tuned in even if they don't join with a comment.
I am impressed and at the very least came away with some good soldering tips for resistors.
Click to expand...

x2
 
ssba said:
Pawned don't feel attacked and thanks for posting your findings and your work process to your results.
I have been lurking waiting to see how this would work out for you and found it very interesting and informative.
I am not presently working on my guages but it is likely I will be soon. I am always glad to see post from folks like yourself who have been their before me to make it easier for us guys that doesn't know where to turn with a repair.
Nice to see your efforts rewarded with a working gauge.
Hope I don't need this repair on my cars, but thanks for sharing even if I don't.
Remember people are on the side lines tuned in even if they don't join with a comment.
I am impressed and at the very least came away with some good soldering tips for resistors.
Click to expand...

Resistors are normally not heat sensitive like semi-conductors are.
I had not intention of pulling the cluster, but the 5vdc regulator I put a few months ago took a dump.
It looks like my soldering was not that great as the input wire was disconnected and still had the solder attached to it.
I had started with the resistors again until I remembered the definition of CRAZY.
Doing the same thing over and over again and expecting different results..

That is when I started thinking about the circuit as a whole and not just the meter.

When I find something that can be fixed and I fail to fix it, I get stubborn and grind on it until I fix it or die, whichever comes first
 
68gtxman said:
I agree with you Mr. 67Dart273, the problem he experienced must be with his specific fuel gauge. This fix should not be appropriate for everyone.

Also, they make variable VRs that can be tweaked to get any range of voltage readings out of them for extra fine tuning, should this help anyone. For example, you may want 5.7 volts to get to the full reading, so after filling the tank, just adjust the variable VR until it reads "full".

I like the way you worked to figure out a solution for your problem. However I would have suggested replacing the gauge with one that had fewer hours it before going thru all the trouble you did. Though maybe your pride (deserved) and satisfaction was worth your efforts. Kudos to you sir!
Click to expand...

Putting in a regulator that cost $1.59 is lots cheaper than a $75 (or more) new gauge
 
I was just thinking, 6vdc was the correct voltage for my car. Yours may work on 6vac but depending on how old/worn out the gauge is you may need a higher voltage. I bought an +8vdc regulator before I had pulled the cluster. I turned out I needed the 6vdc regulator. So I had to run down a 6vdc regulator. The one I bought is only rated for 1 Amp, which is just enough at the resistances in my sending unit of 9.6 ohms full and 76 ohms empty. I am looking for a regulator that can handle more power. This one works but I like the extra current handling capability. So I will find a regulator that can handle more amperage.

If you find the voltage that works on your gauge, divide the voltage by the reading in ohms your sending unit puts out when full.
If you use a single +5vdc for your temp and fuel gauges you will probably be going over the 1 amp rating of the regulator. That is how mine died the other day
 
There are fuel quantity systems that use a variable power source to calibrate the gauge the same way you have done. Search Google for Texas Instruments LM317KCT data sheet. There is a lot of info on it showing how to make a simple and cheap variable power source. Most systems are impossible to calibrate on their full range, so most of them, especially on airplanes, are calibrated to read correctly at empty and not worry about the readings at full (the only time you can have too much fuel, is if you're on fire.)
Until someone makes a plug in system with a microcontroller and a stepper motor indicator, you may only get one point at which the gauge reads correctly.
 
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