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Any body know of a fix for a burned out 6 volt fuel gauge. I have a 51 Chevy 3600, the previous owner converted to 12 volt and in the process fried the gauge.

Thanks,
Rick

I have a fuel guage problem, also. Maybe someone can help us both out. I have a 51 chevy that sat idle for about a year and a half. I recently got it cleaned up and running, but now the fuel guage is always on the full mark when the key is turned on. Any ideas on what to do?
Thanks, Mark

A fuel gauge essentially consists of two windings. One winding (I'll call it the "primary") is independent of the sender unit and it generates a constant force that tends to push the needle to "full". The other coil (I'll call it the "secondary") has the sender unit (and therefore its resistance) in the circuit. When the tank is full, the sender unit has full resistance and little current flows through the secondary coil, allowing the "primary" coil to exert its force and deflect the needle to "F". When the tank is empty, the sender unit is essentially at zero resistance, allowing more current to flow through the secondary coil and it opposes the force exerted by the primary coil, pushing the needle to "E". With all this in mind, the needle could be at "F" because:

-the tank is full.
-the tank is not grounded properly.
-there is a bad connection/open circuit in the wiring going to the sender unit.
-the "secondary coil is open.

For a burned out gauge, I don't know how to fix it. The wire used for the windings is like the diameter of a hair. If you are lucky, the wiring burned out near a terminal and you might be able to resolder.

I don't know if this will apply to your gauges, but I dropped my fuel gauge and broke the coil that runs across the back of the gauge face. I already planned to take it apart, so I used tiny aluminum heatsinks to hold the coil in place and carefully soldered the coil back together. If the coil melted in half, I don't think this solution will work. I was lucky... the break was at the post and it was easy to repair.

I thought that someone posted a note earlier that said that if you fried anything by converting to 12 volt that it would be in the sender unit, not the guage itself, so I'd start with the sender. I have seen 12 volt replacement senders at either ChevyDuty or Kanes?? Not certain if they are a stock item or would be a back-order item. I'm getting ready to put in a resister for my 6 volt sender so hopefully I won't fry anything when I finish my 12 volt conversion! Wish me luck!!

I doubt that the sender could be fried - Jim Carter's sells the same sender for 6 and 12 volt use. The sender isn't even directly hooked to power - the non-ground side runs through the gauge.

T add to GMC's comments, I too doubt the sender is fried. The wire gauge used in the sender unit for resistance is a lot higher (thicker) than the fine wire used to make the coils in the gauge itself. If something got fried with 12 volts, it is likely the "primary" coil I mentioned above that always sees ignition voltage with the key on.

Thanks for the info SoTX, I didn't realize how little I knew until I started reading this forum!
I'll start looking for wiring problems this afternoon.

So where would you suggest I start on mine, a 12v converted 53? My gauge shows permanent full even when dry. What are the steps to getting a reading gauge? What do I change/check first, second, next?

Thanks Guys!!!

Mine always read full as well. I figured it was fried. I got the reducer but it still didn't change the reading. So, I always kept putting in gas. Then for a while I didn't. Sunday I was going to Home Depot and thought, geez the gauge finally totally died. Now it doesn't read anything. Oh well, might as well get some gas...

After gassing up it is reading full again. Not much range but it seems to work after all.

Jake53,

SoTxBoTi stated it nicely. If you gauge goes from Empty to Full when you turn on the ignition, I would bet the gauge is good.

Here are the tests (for the items in SoTxBoTi's list):

-the tank is full. [you have tested this?]

-the tank is not grounded properly. [run a ground wire from the metal fuel tube (clean the metal) that comes out the tank to a good ground - right to the negative lead on the battery]

-there is a bad connection/open circuit in the wiring going to the sender unit. [run a wire from the sender pole on the fuel gauge to the post on the sender unit in the fuel tank]

-the "secondary coil is open. [take the sender unit out of the fuel tank and bench test it]

I hope someone corrects me, if I am wrong. I have done these tests successfully many time but seem to have a hard time describing them correctly.

Good luck,
Tim

So do I need a reducer to get back to 6 volt, and if so, where do I drop it in? Near the sender, near the guage, and on which wires? I will not claim prior knowledge, just a basic understanding.

Pleae continue the lesson master Jedi!

Use the recommended reducer (Runtz) and place it on the "hot" lead that goes into the gauge, not on the sender side of the gauge.

http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=3;t=000663#000000

Tim

I totally support tclederman's comments. Get a Runtz reducer. Though I have limited experience in this area I've been able to get both my truck and another old chevy truck gauge up and running where both were thought to be dead. Unless you actually see a broken wire in the back of the fuel gauge or anything else that even a blind man can see, I'd spend the time going over and over your groundings and connections.

At one point, I was getting really fustrated on my truck and said hey maybe it is the sending unit so I thought I'd install my spare unit into the tank. While removing the old unit and having disconnected all wires to the unit, I thought about one last ditch effort by running a new wire from the sending unit directly to the gauge (runtz already installed). I then ran another new wire grounding the collar of the sending unit to the neg terminal of the battery. Then with the sending unit in my lap, I turned the key to on and guess what? I was able to make the gauge move up and down while raising the sending unit's arm. Suspect? Both old grounding wire and hot wire. It took 3 attempts to get clean contacts but it finally came to life.

Can't say this will work for everyone but.....

One more thought on this full indication ....
The Runtz is a dropping resistor that drops voltage from 12 to 6. I am guessing that there is no current involved in the fuel guage sensing device. If you have a full tank, the sending unit will allow the meter to see 6 volts ....
if you have an empty tank it will see 0 volts ...
if your tank is half full it sees 3 volts, etc.

If you put 12 volts on the guage without a dropping resistor I doubt that anything would fry because there is no current involved. If you do not have a dropping resister and the tank is empty, then the meter will still see 6 volts and think it is full.

You may want to verify that you have a dropping resistor in series. Hope this makes sense.

shoeless,
Hows your better half anyway? Hope you are spoiling her beyond her wildest imagination. Remember what this Sat is....

Took her in for 2 week checkup today and Doc says
she gets the cast off in 4 more weeks. I've concluded that we don't know how much the better half does for us until they can't do anything but operate the remote control and telephone.

Craig is absolutely correct .... remember Saturday !!!