Crazy fuel gauge problem (long post)

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dustertogo

dustertogo

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Never seen anything like this before. 1970 Dart with standard dash. I replaced the fuel gauge because it would stick sometimes when coming up after first cranking. You could bump the dash and the gauge would unstick and go to the correct reading, so I knew it was a gauge and not sending unit problem. I replaced the gauge with one from Classic Industries that was made by Charger Specialties and replaced the voltage limiter with a solid state one from Real Time Engineering. I also replaced the circuit boards with ones from Year One. Now, the fuel gauge pulsates from empty to full in a rhythm(like a metronome). It's like the voltage is switching on and off. Any ideas and help will be appreciated.
 
Difficult. The original gauge setup, the limiter DID pulse, just like a flasher, only faster. You did not see it because the gauge is what is called "heavily damped." Meaning, it takes a short period of time to react and you don't see the pulsing, even though it is there.

Seems to me this could be instability in the limiter, BUT

THE TEMP GAUGE (and oil gauge in a Ralleye cluster) all use the same limiter voltage. So if your temp gauge works OK, it has got to be a defective fuel gauge unit.

Only way I could see the sender causing pulsing is, if the fuel is sloshing, AND the gauge is not damped enough
 
67Dart273 said:
Difficult. The original gauge setup, the limiter DID pulse, just like a flasher, only faster. You did not see it because the gauge is what is called "heavily damped." Meaning, it takes a short period of time to react and you don't see the pulsing, even though it is there.

Seems to me this could be instability in the limiter, BUT

THE TEMP GAUGE (and oil gauge in a Ralleye cluster) all use the same limiter voltage. So if your temp gauge works OK, it has got to be a defective fuel gauge unit.

Only way I could see the sender causing pulsing is, if the fuel is sloshing, AND the gauge is not damped enough
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Yes, I did forget to mention that the temp gauge seems to work just fine.
 
I has a similar problem with a gas gage. I replaced the sending unit and the gage would peg. Although the part numbers were correct they were from different manufactures. So it might be the two units, gage and sender are not compatible.
 
if I'm not mistaken the classic replacement gauge says it has to be used with a solid state IVR. Maybe the ivr you are using is acting too much like a mechanical unit.

Screenshot_20201127-125436.png
 
Dana67Dart said:
if I'm not mistaken the classic replacement gauge says it has to be used with a solid state IVR. Maybe the ivr you are using is acting too much like a mechanical unit.

View attachment 1715637956
Click to expand...
Yes, thanks. I'm using the solid state IVR from Real Time Engineering. But it is acting like a mechanical unit it seems, with voltage pulsing. I'm stumped.
 
I am not for sure but don't you bend the limit switch, the bi-metal arm in the gas gauge if you use the solid state? I have to find the web site and check.....?
 
Dicer said:
I am not for sure but don't you bend the limit switch, the bi-metal arm in the gas gauge if you use the solid state? I have to find the web site and check.....?
Click to expand...

That is only Ralleye cluster, which has the OEM IVR built inside the fuel gauge. He seems to have a "standard" cluster which uses external limiter
 
Any chance the capacitor still needs to be in the cir to level out the voltage?

Also just spitballing
 
I thought the RTE IVR was built to electronically mimic the old off/on switching of the mechanical limiter. Your new fuel gauge may be looking for a smooth DC wave from a truly electronic voltage limiter.
 
Dana67Dart said:
Any chance the capacitor still needs to be in the cir to level out the voltage?

Also just spitballing
Click to expand...

The cap is for radio noise suppression on the old style. It is not large enough capacity to act as a filter in this sense.
 
I know the RTE unit mimics the original limiter in higher output for faster gauge warmup at switch on. I dont think it mimics the limiters continuous pulse. It has fault sensing in it. If it were sensing a fault and switching on and off you should see this in the temp gauge too, providing you have hot water, a hot temp sender.
 
RedFish said:
I know the RTE unit mimics the original limiter in higher output for faster gauge warmup at switch on. I dont think it mimics the limiters continuous pulse. It has fault sensing in it. If it were sensing a fault and switching on and off you should see this in the temp gauge too, providing you have hot water, a hot temp sender.
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The temp gauge is rock steady and appears to be reading where it always does. That's why I'm stumped!
 
The only thing left is what all is common to the fuel gauge. That is, the wiring and the fuel sender, and the gauge itself. I would find/ get some substitute resistors to hook up to the sender wire, and see what that gets you. If nothing changes, "one last thing" would be to pull cluster and check connections to the gauge, follow the path. Follow from the IVR to the gauge, make sure the gauge studs are tight, follow back to the harness connector, and then check out the sender wires.

If that is all OK, there is only one thing left and that is the gauge itself.
 
67Dart273 said:
The only thing left is what all is common to the fuel gauge. That is, the wiring and the fuel sender, and the gauge itself. I would find/ get some substitute resistors to hook up to the sender wire, and see what that gets you. If nothing changes, "one last thing" would be to pull cluster and check connections to the gauge, follow the path. Follow from the IVR to the gauge, make sure the gauge studs are tight, follow back to the harness connector, and then check out the sender wires.

If that is all OK, there is only one thing left and that is the gauge itself.
Click to expand...
67Dart273 said:
The only thing left is what all is common to the fuel gauge. That is, the wiring and the fuel sender, and the gauge itself. I would find/ get some substitute resistors to hook up to the sender wire, and see what that gets you. If nothing changes, "one last thing" would be to pull cluster and check connections to the gauge, follow the path. Follow from the IVR to the gauge, make sure the gauge studs are tight, follow back to the harness connector, and then check out the sender wires.

If that is all OK, there is only one thing left and that is the gauge itself.
Click to expand...
Sounds like a plan. I’ll definitely give it a try. Thanks.
 
I have a question .when i fill my 66 Dart with gas the gauge goes to full after a few miles of useing gas it goes down to empty .could it be the voltage limiter .all the other gauges work properly ,thanks
 
Paul King said:
I have a question .when i fill my 66 Dart with gas the gauge goes to full after a few miles of useing gas it goes down to empty .could it be the voltage limiter .all the other gauges work properly ,thanks
Click to expand...
You should start a new thread
 
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