69 charger fuel gauge is goofy
#2635149
03/21/19 11:00 AM
03/21/19 11:00 AM
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Joined: Mar 2007
Posts: 12,013 Finally a HUSKER again
Moparnut426
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OP
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Heres what its doing...
This car has a Tanks Inc EFI Tank, and its got the correct fuel sender in the tank. I grounded the sender to the chassis,
Now. Key on, with roughly 5 gallons in the tank it reads just over 1/4 tank. As soon as I turn the Dash lights on, Headlights on, and thumb wheel is turned on for back lights. The fuel gauge will go to zero. I have put a solid state voltage limiter in the cluster.
Heres what I have done to correct the issue.
Cleaned every ground. made several extra straps for ground. Ran a ground from the battery to the sender, tried OE sender, has new fuel gauge in the cluster, cleaned circuit board contacts. tested board, made a ground from cluster to dash frame, cleaned ground from frame to column, tried different thumb wheel dimmer switch. all have same issue, as soon as back lights in cluster come on the fuel gauge drops to zero.
I tried a different voltage limiter and with that limiter it will peg to full when back lights are on. I can wiggle the limiter and get no change. Ive tried to check power behind the dash but its very difficult to get my scrawney ass back there to test, but Im going to grab some alligator clamps for my DVOM and test again. I thought maybe the battery was low, so I ran the test with 13 volts from my charger on it and it did exactly the same thing........
ANY POINTERS, will be greatly appreciated. New dash harness, New engine harness, new forward lighting harness.....
Thanks in advance
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Re: 69 charger fuel gauge is goofy
[Re: Andrewh]
#2635194
03/21/19 12:19 PM
03/21/19 12:19 PM
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Joined: Mar 2007
Posts: 12,013 Finally a HUSKER again
Moparnut426
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That is odd you get a different result from a different voltage reg. is it the back up VR solid state as well or the old style?
Can you measure the output of the vr with and without the lights on? see if it is cutting out?
It isn't the sending unit, so it must be the dash.
Can you add a ground directly from the battery to the frame? or even the cluster. The bolts that hold it to the frame should be the ground.
If that solves it, then it is just bad grounds. I would see if the column got insulated some how and isn't grounding as expected. I have added a ground strap from the cluster to the dash frame. I have 3 solid state regulators, and it acts the same with them all. I have a different board with the VL built into the dash coming for a different dash im working on for a friend. I might swap that and try it. And I have used 3 standard Voltage Limiters, and honestly got different readings on them all, but they could easily have been crappy as they were in my box of spare junk.....
Last edited by Moparnut426; 03/21/19 12:33 PM.
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Re: 69 charger fuel gauge is goofy
[Re: Moparnut426]
#2635221
03/21/19 01:37 PM
03/21/19 01:37 PM
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Joined: Jan 2003
Posts: 15,526 Omaha Ne
TJP
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I am thinking you may have a ground issue somewhere in the lighting circuit as things appear fine until you turn the lights on. The lights may be grounding through the instrument cluster thereby causing your problem. You can try to identify which circuit is at fault by disconnecting the body harness at the Kick panel area or forward lamp harness along the fender well. It may also be the instrument lights themselves not getting a good ground, Pull the fuse. Try the above 3 things and see if one makes the problem go away. You will then know if it is the lighting circuit and if so which one let us know
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Re: 69 charger fuel gauge is goofy
[Re: TJP]
#2635227
03/21/19 01:57 PM
03/21/19 01:57 PM
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Joined: Mar 2007
Posts: 12,013 Finally a HUSKER again
Moparnut426
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I Live Here
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I am thinking you may have a ground issue somewhere in the lighting circuit as things appear fine until you turn the lights on. The lights may be grounding through the instrument cluster thereby causing your problem. You can try to identify which circuit is at fault by disconnecting the body harness at the Kick panel area or forward lamp harness along the fender well. It may also be the instrument lights themselves not getting a good ground, Pull the fuse. Try the above 3 things and see if one makes the problem go away. You will then know if it is the lighting circuit and if so which one let us know Just to clarify, it does it when the dash lights are turned on via thumb wheel dimmer switch. It wont do it with the lights on. I can turn the lights on, have the thumb wheel to off, and it all works fine, as soon as you move the thumb wheel and theres just a very light glow of back lighting in the cluster the gauge goes to dead empty. Kinda why I thought I had a bad switch. but nope on that one....
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Re: 69 charger fuel gauge is goofy
[Re: Moparnut426]
#2635237
03/21/19 02:27 PM
03/21/19 02:27 PM
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Joined: Jan 2003
Posts: 15,526 Omaha Ne
TJP
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I Live Here
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Just to clarify, it does it when the dash lights are turned on via thumb wheel dimmer switch. It wont do it with the lights on. I can turn the lights on, have the thumb wheel to off, and it all works fine, as soon as you move the thumb wheel and theres just a very light glow of back lighting in the cluster the gauge goes to dead empty. Kinda why I thought I had a bad switch. but nope on that one....
That would be a pretty strong indicator that the ground for the instrument lights is the issue and it is most likely robbing the ground from the voltage limiter /gauges.
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Re: 69 charger fuel gauge is goofy
[Re: Moparnut426]
#2635238
03/21/19 02:28 PM
03/21/19 02:28 PM
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Joined: Jan 2003
Posts: 10,759 North Dakota
6PakBee
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You can read the output voltage of the IVR at either the oil pressure sender or the temperature sender. Try that in both a headlights on and headlights off state.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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Re: 69 charger fuel gauge is goofy
[Re: topside]
#2635262
03/21/19 03:19 PM
03/21/19 03:19 PM
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Joined: Jan 2003
Posts: 15,526 Omaha Ne
TJP
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I Live Here
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Interesting. I'm battling a similar deal but not a gas gauge, it's related to the thumbwheel dimmer/IP lights. Mess with the thumbwheel trying to make the IP lighting work, POP goes the parklamp & brake light fuse. Jumping the IP fuse from another accy feed at the fuse box, same thing. Dome light works fine, everything else fine. Those dimmer thumbwheels are notorious, tempted to replace it with a rebuilt OEM unit, but whatta PITA. Just occurred to me to try a 2nd ground at the tail lamps... If your blowing the fuse either the switch is shorted or you have a short somewhere in the circuit. Take the switch out and clean it thoroughly, then test with and Ohm meter. One could also bypass the switch at the plug with a jumper and see if the fuse still blows. If it does, its not the switch
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Re: 69 charger fuel gauge is goofy "FIXED"
[Re: moparx]
#2635571
03/22/19 12:51 PM
03/22/19 12:51 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Agreed, What my Omaha partner in crime said, ground issues are the worst of the worst!
live every 24 hour block of time like it's your last day on earth
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