gas gauge wireing

Thanks, Vic. I sent you a email.

Hey guys,,, I have at least two dozen of them or more here,,,, been grabbing them for years.
vic

Update, got new cvr installed and have the 12v to 5v working now. Last time I messed with this the gauge worked with 2 aa battries hooked to both posts. Now when I tried the battery test , the gauge no longer works. Tried grounding the wire from the sender and still wont work so I guess my gauge is now shot. Any one know where to get a new gauge or a fix for the old one? Thanks.

I have a BOX full of them,,,, Been BAD sick and the putter was too,,, both back up and running.
PM me and I can drop one or two in the mail, nbd,,,
ALL of the "so called" senders are actually variable grounding units,,, the more the ground the higher the reading on the gauge. Like posted the connectors on the resistor are different ON PURPOSE in order to not burn it up. The ground is accomplished (by my previous statement) by the sending unit and a QUICK (as in quick, not prolonged) is to simply ground the sending unit side of the gauge with the key on. The 12 to 14.2 volts incoming and a PIG TAILED black wire that goes to each gauge to supply the reduced (pusating) reduced voltage to each gauge.
If you ground the output side of the resistor you will burn it up,, the grounding needs to be controlled by the sending units. IE: my statement about simply grounding the sending unit side of the gauge. If when you ground it and the gauge climbs all the way up that means that the supply voltage is geting there and the problem is in the grounding side of the circuit. IE: bad sending unit or bad wiring.
The gas tank is designed to accomplish the final grounding, meaning that if you do not have a good ground contact between the top of the gas tank to the frame it will not work as there is not final grounding,, etc,,,etc,,,
Old Skool

Doesn't one wire go to the temp gauge

Ok Im working on the gas gauge again. Did the 4 tests in the post above. 12 volts in to the cvr steady 5 volts out ,not pulsing. gas gauge didnt work with the 2 battries jumped across, but if you hit it real quick with 12 volts goes to full real fast. Disconnected sending unit wire and grounded to frame, turned key, nothing on gauge. Ran new wire from sending unit to gauge hit key, went to full real slow. I have 5 gallons of gas in the tank as I just pulled tank to clean and put in a new sending unit. Also installed new ground from engine to frame and new ground from sender to frame like in above post. What am I missing ? Thanks

Ok,,,,,,ignition switch sends 12 volts to that current regulator,,,,,,and IF,,,,it is GROUNDED, it sends out 5 volts to the gas and temperature gauges,,,,,the gas sending unit sends a 10 ohm signal to the gauge when the tank is FULL,,,,,73 ohms if the tank is EMPTY,,,,,,,,quick tests would be you take a 12 volt test light, with the key on, and one terminal of the current limiter will make the test light glow bright, the other should blink,,,,,,,,take off the wire on the fuel gauge terminal that comes from the sending unit,,,gauge should go to EMPTY,,,,,,grounding that terminal should make the gauge read FULL,,,,,,,,see what you find,,,,,,,

Slow gauge- Nine times out of ten it's a weak ground or dirty leads. As Don is indicating the sender must be in spec 10-73 ohm. BTW the pulsing voltage only shows on analog VM's at a sensitive setting/range.

So, the gauge itself is suspect, since it takes a big jolt to make it jump (should jump pretty quick with 5 gal in the tank,) and batteries did nothing. If not the gauge the sender may be dirty or worn, needing more voltage to react, and higher resistance than spec range.

Try again using the small batteries, clean wire, clean contacts to the gauge. Share the results.

Measure the resistance of the sender (hand held, out of tank is best, you need to swing it through the
range of E to F.)

Good luck!

Best regards,
George

The sender and wires are new, ran a 2nd wire to ground to frame like you showed. bypassed the wire from sender to gauge and ran a new one as I got no movement with the original. Just cant figure why it goes to full when I only have 5 gallons in it. Watching ebay for a new gauge , no luck yet.

but the deal is,,,,, is it the CORRECT sending unit,,,,,,,and DOES IT WORK,,,,,,,,pull it out,,,,,,measure the ohms between the terminals,,,,,,,with the float hanging down, you should get 73 ohms,,,,,,pull that float up to FULL and you should get 10 ohms,,,,,1/2 should read about 40,,,,,,,,see what you get,,,,,,

Agreed, I cannot trust the sender units out there, they will look to be a perfect match but the filament diameter or winding count will be out of spec. If you cannot get 10 to 73 (have very clean contact to your meter,) and like Don suggests, about 40 ohms @ half range, then the sender is not the right one or faulty.

The sending unit is correct according to C &G ford parts where I got it. If its working right, who knows. Im going to admit I have no idea how to check ohms, where do I connect the test leads ? Im  done messing with it till Mon. Ill update then. Thanks.

Set your meter to ohms in the 0-100 range if possible. With the sender wire disconnected, put the red lead to the sending wire terminal on the sending unit and put the black lead to the senders mounting plate and see what you get. Then put the black lead to the chassis, and see if it's the same reading or near the same. Make sure you are getting good contact with your leads. Check it empty or near empty, then check it full and report back The ohms setting on you meter is measuring resistance between those 2 point through you leads.

Btw, before you do the test, set your meter to ohms and hold the leads together and note the reading, subtract this # from your measurements.

You said you had a steady 5 volts out (of the cluster voltage regulator), yet it should be 5 volts pulsating

when you hook up an ohm meter to the wire post and the base of the sending unit, you should get 10 ohm reading when you move the float up to FULL,,,,about 40 at 1/2,,,,,,,73 when down to EMPTY,,you are just testing each piece in the system to see if they are doing their job,,,,, , or if SOMEONE put 12 volts to it and wrecked it,,,,

I tested the old gauge I removed ,got 97 empty and 37 full. Very hard to get a steady reading. I m going to drive most of the gas out before I test the new one just to see if the gauge goes down any and Im tired of draining gas.

those readings are high,,,,,,the gas gauge would not like it,,,,,,,,the contact and wire strip are dirty,,,,
you might be able to sand it clean to make good contact again,,,,,,,,

Ok , Part of my problem is that I m a dumb ass .I hooked my 2nd ground to frame wire onto the same post as the sending unit wire, thats why the gauge went to full. unhooked that wire and no reading at all like when I started. Since my gauge didnt work with the two batteries I guess its bad. Pulled the sending unit and got 58 ohms empty 28 half way and 10 full. If I find a new gauge how far off will it read?

the gas gauge thinks 58 ohms is like 1/4 full,,,,,,,,you gots to have more ohms for the gauge to get down to EMPTY,,,,,,,so according to your readings, your tank is Empty when the gauge reads 1/4,,,,,,but how accurate is your meter? Ohms are REAL sensitive especially if you are measuring a variable resistor like what is in the sending unit,,,,,best deal is, put the wires on the sending unit, hold it in your hand, turn the key on, see what the gauge does as you move the float,,,,,the float dont lie, you can move it and see if the gauge agrees,,,,,I surely like if the gauge reads EMPTY and I got a couple of gallons left in the tank,,,,,

so you shorted out the gauge and current limiter,,,,,,does the current limiter pass the blinking test light test,,,,,,,,the less you mess with this thing, the better off you will be,,,,,

Is that the regulator that takes it down to 6v? You think he screwed it up when he ran 12 volts in there somewhere on the other side?

I agree, I think you're going to have to pull that damn thing out and manipulate it by hand. lol

Ford and Dodge had this wonderful idea to use 6 volt gauges,,,,,,probably had them leftover from the 40's,,,,,,,,,so they use this current limiter/voltage regulator to drop the 12 volts down to 6 or so,,,,,I am just pointing out the possible scenarios that he has,,,,,12 volts starts at the ignition switch, gets cut down to 5,,,,,goes through the gauge,,,,then the sender,,,,,,but the sender has 10 ohms resistance in it so it prevents the full voltage from flowing through the circuit,,,,,if he grounded the post on the sending unit, that is 0 ohms, a dead short to ground,,,,,,so the gauge and the current limiter were shorted out,,,,,now the question is, did they survive,,,,,,,thats why he needs to run some tests,,,,,,but this is a good topic,,,,we sure are finding some good information about fuel gauges,,,,,,,

,,,,and we are talking about,,,, IF,,,,,,he shorted the wire that comes from the gauge to ground,,,,,either by connecting it somewhere else or hooking a ground wire to it,,,,,,

I checked the cvr with a test light, bright light in, dim light out but not pulsing. Was reading 12 in and 5 out, guessing it's still good. I wonder if the tank is grounded to the frame. It has rubber under the straps and foam on top so it won't rub the weight above the tank. Still thinking the gauge is bad although it still goes to full when grounded.

another thing is the current limiter has to be grounded,,,,,,if you remove the instrument panel and let it hang, it aint grounded anymore,,,those screws that hold the panel to the dash are the ground,,,,,,so you use a jumper wire to ground the instrument panel to the dash to run your tests,,,,,,can you get the test light to blink on the post of the fuel gauge if you disconnect the wire on it that goes back to the tank,,,,,,also remove that temperature gauge wire too,,,for the test,,,,,,