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#1 |
Registered User
Join Date: Jan 2017
Location: Nashville, TN
Posts: 2
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Dancing Gas Guage
My '72 has a fuel gauge that is stable when it's sitting still, but when I'm driving will move up and down. At lower speeds the swing is about a 1/4 to 1/2 a tank either way, but it increases at highway speeds and will swing from empty to beyond full. My first thought was the sending unit since it still had the original in it. I replaced the sending unit, but I still have the problem. Thoughts?
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#2 |
Registered User
![]() Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: Dancing Gas Guage
I too have the exact same problem. I replaced the sending unit and still have the issue. I also went through and checked all my grounds including the one for the dash.
Same thing, stumped???? Could this be the resistor on the back of the fuel gauge? I might add that I have dash bulb out on that side of the cluster. Any suggestions out there??? That little bouncy thing is on my nerves...... |
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#3 |
Senior Member
![]() Join Date: Aug 2013
Location: Ca. <-> Ma.
Posts: 5,709
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Re: Dancing Gas Guage
I'll be watching this one!
I've got a truck that does this too. Hopefully someone has some info |
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#4 |
Senior Member
![]() Join Date: May 2010
Location: Wisconsin & Arizona
Posts: 4,844
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Re: Dancing Gas Guage
I had that problem a couple years ago after I installed a used tach cluster. Replacing the gauge with the one from my original cluster fixed the problem. The one that bounced had very little resistance to being rotated. Just blowing on the needle made it spin. The one I replaced it with barely moved when I blew on it. Works like it should now. There is apparently some sort of damping mechanism that keeps the gauge stable as the gas sloshes around in the tank.
Last edited by FirstOwner69; 06-19-2017 at 03:08 PM. |
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#5 |
Moderator
![]() Join Date: May 2007
Location: Southern Cal
Posts: 20,004
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Re: Dancing Gas Guage
Follow the wire from your sending unit to the fuse panel. There's a good chance it has a wear spot somewhere along the way, usually under the door threshold guard that it passes under.
__________________
1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#6 |
Registered User
![]() Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: Dancing Gas Guage
I will look at this again and report back. May even substitute a new wire in there for positive diagnosis! Thank you!
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#7 |
Senior Member
![]() Join Date: May 2010
Location: Wisconsin & Arizona
Posts: 4,844
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Re: Dancing Gas Guage
I know the wiring is a common problem, but I don't believe the gauge would be stable when sitting still and only bounce when being driven if wiring were the problem. Worth a shot though. Certainly less costly than replacing the gauge.
EDIT: Here's a thread where I summarized my fuel gauge troubleshooting as mentioned in my post above. http://67-72chevytrucks.com/vboard/s...d.php?t=672327 Last edited by FirstOwner69; 06-19-2017 at 04:43 PM. |
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#8 |
Registered User
Join Date: Jan 2017
Location: Nashville, TN
Posts: 2
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Re: Dancing Gas Guage
I finally located the cause of the mystery dancing gauge! A PO had replaced the wire to the sending unit, and apparently ran the wire too long. His solution? He wrapped it several times around the dashboard wiring harness bundle by the fuse block. The wrapped wires were acting like a current transformer and current flowing through the harness induced voltage in the fuel gauge wire. I uncoiled the unintended miniature CT, and now the gauge works just fine!
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#9 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,621
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Re: Dancing Gas Guage
Thanks for the follow-up (which unfortunately seems to be all too rare)! That sure is one for the books. I doubt many others will have the same problem but ya never know!
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__________________
- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#10 |
Registered User
![]() Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: Dancing Gas Guage
This one still has me stumped. I have checked the brown wire from the tank all the way to the fuse panel.
I have decided to wait to look further into the dash at this point. I am still bummed about the ex smashing my NOS gauge I had stashed. UGH! ![]() |
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#11 |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,713
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Re: Dancing Gas Guage
__________________
VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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