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Gas gauge or voltage limiter

ram250098

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My gas gauge was going up and down all weekend. At one point it would start to rise the snap back to empty. It did this a few times then would rise to full slowly and back to half full slowly. Now it reads empty all the time. I put a test light on the voltage limiter and have power. I grounded the blue wire at the tank and the gauge did nothing. I put the test light to both connections at the back of the gauge and nothing. I thought one of the wires would have power, so I am not sure if it is the gauge or the voltage limiter. I think the sender is ok because it was moving the gauge.
Any ideas?
The car is a 73 Charger with the rallye dash.
Thanks
AL
 
If the voltage limiter is the problem, the oil and temp gauges would be doing the same thing.

Don't forget that the gauge could have poor connections at the PC board.

Other than that, it's a simple matter of elimination. Connections at the gauge, connections at the pck board connector, the connection in the kick panel for the rear harness, poor ground at the sender, bad sender to wire connection, or just bad sender.

Go down to Radio shack and buy some resistors, watch the gauge for a few miles with a resistor subbed for the sender. IF the gauge settles to a steady reading, you know the trouble is right at the sender. Resistances are (I'd go for the 1/2 tank one):

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

If you buy 4 - 100 ohm 1/2 watt resistors, wire them all in parallel, that will give you 20 ohms, close enough. That will also give you enough power dissipation that they won't heat over time.
 
Well I'm no expert, but I did just spend two hours standing on my head under my dash. My gas gauge has been reading full for quite awhile and just recently while driving the car, my oil,temp and gas gauges all stopped working. After shutting the car off for a time and then restarting, the gauges would come back on. When I checked the voltage on the limiter, the readings were all over the place (sometimes 4 volts or full 12 volts). So I just got a solid state limiter off E-bay and it came with only 2 terminals. I started to send it back because it definitely wasn't the one in the picture, but with a couple of jumpers, I was able to make it work... Except that the gas gauge still shows full. I'm going to try the resister check. Thanks.
 
Well I'm no expert, but I did just spend two hours standing on my head under my dash. My gas gauge has been reading full for quite awhile and just recently while driving the car, my oil,temp and gas gauges all stopped working. After shutting the car off for a time and then restarting, the gauges would come back on. When I checked the voltage on the limiter, the readings were all over the place (sometimes 4 volts or full 12 volts). So I just got a solid state limiter off E-bay and it came with only 2 terminals. I started to send it back because it definitely wasn't the one in the picture, but with a couple of jumpers, I was able to make it work... Except that the gas gauge still shows full. I'm going to try the resister check. Thanks.

If it is showing full it may be a cracked wire coming from the sender to the dash grounding out somewhere along the way. My money is in the trunk.
 
I was thinking it was because of too much voltage because of the limiter spitting 12 volts. I disconnected the wire at the sender and the fuel gauge went to empty. Looks like I had 2 problems and I'm in need of a new sender. (It was close to the trunk) Thanks.
 
It's been one hell of a long time since I was into a B body Ralley dash. But the same principles apply. You have to SUSPECT any part of the "system" from one end to the other.

Here's what all was wrong with my 67 Dart, just as an example. Even I was impressed as I got deeper into this

1 The pins for the cluster connector were either loose or broken clear off. Mine was in such bad shape that I abandoned the connector, soldered wire pigtails to the board traces, and installed two "Molex" style connectors from Radio Shack

2 The VR was bad

3 The VR "socket" was bad. On mine, there are brass spring fingers which were not making contact with the board traces. I had to solder jumpers between the spring fingers (contacts) and the board traces

4 The studs on one gauge were corroded and not making contact. I replaced the fake nuts with real ones. Work them "tight/ loose/ tight" to scrub the board clean

5 The temp sender turned out to be either bad or the wrong sender

6 The fuel gauge is still not accurate, but at least it's "predictable"

and LAST remember THIS. These things are ??how?? old now? Those gauge movements THEMSELVES are suspect for any accuracy they ever had.
 
I have the plug in terminals on the back of the rallye dash not the pc board. I put my volt meter inside both connections to the gauge and it showed no voltage at all, so I think it has to be the limiter.
AL
 
i thought the limiter affected the whole dash?ar'nt your other guages fine?
 
if you grounded the wire to the gauge (from the sending unit) and with the key on, the gauge didn't move...it would lead Me to believe the gauge is bad...but....I would make sure the tank and sending unit have a good ground
 
I did ground the wire from the tank and the gauge did nothing, but wouldn't that only work if it had power to it. If the limiter is not sending power to the wire then grounding the sender would show nothing.
Both wires to the gauge have 0 power.
AL
 
I did ground the wire from the tank and the gauge did nothing, but wouldn't that only work if it had power to it. If the limiter is not sending power to the wire then grounding the sender would show nothing.
Both wires to the gauge have 0 power.
AL
if you have no power to guage then it is not the guage.trace the power lead wire and check for breaks,or bad contact points.
 
Thanks 67 Coronet. Not much to trace. The voltage limiter is right beside the Fuel gauge.
I have full 12 volts to the limiter but no power at either contact to the gauge. I thought at least one of the points should have 5 volts. Because I have no power at all it should be the limiter correct?
AL
 
i thought the limiter affected the whole dash?ar'nt your other guages fine?
I don't think you ever answered this, but on my dash the temp guage is fed first. When my fuel gage went to empty, my other guages also stopped working. I would think that if your other guages are working and you have no power to fuel guage, you would have a broken wire or bad connection. If other gauges are not working I would take the limiter out, apply power to ignition side and measure voltage coming out.
 
Thanks wahya. My other gauges have been disconnected in place of mechanical ones. But I did test the connections with the volt meter and have no power there as well.
The limiters power in is getting full 12 volts but nothing to the gauges. Like I said in the first post at one point the gauge would start to rise the drop very fast like turning of a light fast...did that a few times then nothing.....could it have just blown inside/
Al
 
Go down to Radio shack and buy some resistors...if you buy 4 - 100 ohm 1/2 watt resistors, wire them all in parallel, that will give you 20 ohms, close enough...

Actually, it is 25 Ohms.

Rt=1/((1/r1)+(1/r2)+(1/r3)+(1/r4))

Each resistor is 0.01, and four are 0.04. Take the reciprical, and that is 25 Ohms.

Dont forget to check the ground strap on the feul line to sender at the tank.
 
Actually, it is 25 Ohms.

Rt=1/((1/r1)+(1/r2)+(1/r3)+(1/r4))

Each resistor is 0.01, and four are 0.04. Take the reciprical, and that is 25 Ohms.

Dont forget to check the ground strap on the feul line to sender at the tank.

I can't type. I knew that. And you don't need fancy formulas, either. For equal resistances, all yu' need ta do is divide by 4

I learned the resistor code before political correctness was even a word LOL
 
That is what I figured..bad limiter. I got another of a buddy of mine.
Put the limiter in and she moves to empty and thats it...but it does move more that before *g*. I grounded the wire to the tank and the gauge reads full so the gauge must be ok. I am getting power to both sides of the limiter. 12 Volts to one side and 5 to the other..the 5 volts is not constant it pulses which I think that is what it is supposed to do. Could it be the sending unit in the tank be pooched..seems odd the limiter would go same time as the sender.
AL
 
Do you have a ground strap straddling the rubber line from the sending unit to the hard line going to the pump? If not add one, if there is one there try cleaning up the contact surfaces.
 

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